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freebsd-skq/sys/vm/vm_phys.c

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Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
/*-
* Copyright (c) 2002-2006 Rice University
* Copyright (c) 2007 Alan L. Cox <alc@cs.rice.edu>
* All rights reserved.
*
* This software was developed for the FreeBSD Project by Alan L. Cox,
* Olivier Crameri, Peter Druschel, Sitaram Iyer, and Juan Navarro.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
* WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_ddb.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/queue.h>
#include <sys/sbuf.h>
#include <sys/sysctl.h>
#include <sys/vmmeter.h>
Change the management of cached pages (PQ_CACHE) in two fundamental ways: (1) Cached pages are no longer kept in the object's resident page splay tree and memq. Instead, they are kept in a separate per-object splay tree of cached pages. However, access to this new per-object splay tree is synchronized by the _free_ page queues lock, not to be confused with the heavily contended page queues lock. Consequently, a cached page can be reclaimed by vm_page_alloc(9) without acquiring the object's lock or the page queues lock. This solves a problem independently reported by tegge@ and Isilon. Specifically, they observed the page daemon consuming a great deal of CPU time because of pages bouncing back and forth between the cache queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of this problem turned out to be a deadlock avoidance strategy employed when selecting a cached page to reclaim in vm_page_select_cache(). However, the root cause was really that reclaiming a cached page required the acquisition of an object lock while the page queues lock was already held. Thus, this change addresses the problem at its root, by eliminating the need to acquire the object's lock. Moreover, keeping cached pages in the object's primary splay tree and memq was, in effect, optimizing for the uncommon case. Cached pages are reclaimed far, far more often than they are reactivated. Instead, this change makes reclamation cheaper, especially in terms of synchronization overhead, and reactivation more expensive, because reactivated pages will have to be reentered into the object's primary splay tree and memq. (2) Cached pages are now stored alongside free pages in the physical memory allocator's buddy queues, increasing the likelihood that large allocations of contiguous physical memory (i.e., superpages) will succeed. Finally, as a result of this change long-standing restrictions on when and where a cached page can be reclaimed and returned by vm_page_alloc(9) are eliminated. Specifically, calls to vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and return a formerly cached page. Consequently, a call to malloc(9) specifying M_NOWAIT is less likely to fail. Discussed with: many over the course of the summer, including jeff@, Justin Husted @ Isilon, peter@, tegge@ Tested by: an earlier version by kris@ Approved by: re (kensmith)
2007-09-25 06:25:06 +00:00
#include <sys/vnode.h>
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
#include <ddb/ddb.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_kern.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_phys.h>
struct vm_freelist {
struct pglist pl;
int lcnt;
};
struct vm_phys_seg {
vm_paddr_t start;
vm_paddr_t end;
vm_page_t first_page;
struct vm_freelist (*free_queues)[VM_NFREEPOOL][VM_NFREEORDER];
};
static struct vm_phys_seg vm_phys_segs[VM_PHYSSEG_MAX];
static int vm_phys_nsegs;
static struct vm_freelist
vm_phys_free_queues[VM_NFREELIST][VM_NFREEPOOL][VM_NFREEORDER];
static int vm_nfreelists = VM_FREELIST_DEFAULT + 1;
static int cnt_prezero;
SYSCTL_INT(_vm_stats_misc, OID_AUTO, cnt_prezero, CTLFLAG_RD,
&cnt_prezero, 0, "The number of physical pages prezeroed at idle time");
static int sysctl_vm_phys_free(SYSCTL_HANDLER_ARGS);
SYSCTL_OID(_vm, OID_AUTO, phys_free, CTLTYPE_STRING | CTLFLAG_RD,
NULL, 0, sysctl_vm_phys_free, "A", "Phys Free Info");
static int sysctl_vm_phys_segs(SYSCTL_HANDLER_ARGS);
SYSCTL_OID(_vm, OID_AUTO, phys_segs, CTLTYPE_STRING | CTLFLAG_RD,
NULL, 0, sysctl_vm_phys_segs, "A", "Phys Seg Info");
static void vm_phys_create_seg(vm_paddr_t start, vm_paddr_t end, int flind);
static int vm_phys_paddr_to_segind(vm_paddr_t pa);
static void vm_phys_split_pages(vm_page_t m, int oind, struct vm_freelist *fl,
int order);
/*
* Outputs the state of the physical memory allocator, specifically,
* the amount of physical memory in each free list.
*/
static int
sysctl_vm_phys_free(SYSCTL_HANDLER_ARGS)
{
struct sbuf sbuf;
struct vm_freelist *fl;
char *cbuf;
const int cbufsize = vm_nfreelists*(VM_NFREEORDER + 1)*81;
int error, flind, oind, pind;
cbuf = malloc(cbufsize, M_TEMP, M_WAITOK | M_ZERO);
sbuf_new(&sbuf, cbuf, cbufsize, SBUF_FIXEDLEN);
for (flind = 0; flind < vm_nfreelists; flind++) {
sbuf_printf(&sbuf, "\nFREE LIST %d:\n"
"\n ORDER (SIZE) | NUMBER"
"\n ", flind);
for (pind = 0; pind < VM_NFREEPOOL; pind++)
sbuf_printf(&sbuf, " | POOL %d", pind);
sbuf_printf(&sbuf, "\n-- ");
for (pind = 0; pind < VM_NFREEPOOL; pind++)
sbuf_printf(&sbuf, "-- -- ");
sbuf_printf(&sbuf, "--\n");
for (oind = VM_NFREEORDER - 1; oind >= 0; oind--) {
sbuf_printf(&sbuf, " %2.2d (%6.6dK)", oind,
1 << (PAGE_SHIFT - 10 + oind));
for (pind = 0; pind < VM_NFREEPOOL; pind++) {
fl = vm_phys_free_queues[flind][pind];
sbuf_printf(&sbuf, " | %6.6d", fl[oind].lcnt);
}
sbuf_printf(&sbuf, "\n");
}
}
sbuf_finish(&sbuf);
error = SYSCTL_OUT(req, sbuf_data(&sbuf), sbuf_len(&sbuf));
sbuf_delete(&sbuf);
free(cbuf, M_TEMP);
return (error);
}
/*
* Outputs the set of physical memory segments.
*/
static int
sysctl_vm_phys_segs(SYSCTL_HANDLER_ARGS)
{
struct sbuf sbuf;
struct vm_phys_seg *seg;
char *cbuf;
const int cbufsize = VM_PHYSSEG_MAX*(VM_NFREEORDER + 1)*81;
int error, segind;
cbuf = malloc(cbufsize, M_TEMP, M_WAITOK | M_ZERO);
sbuf_new(&sbuf, cbuf, cbufsize, SBUF_FIXEDLEN);
for (segind = 0; segind < vm_phys_nsegs; segind++) {
sbuf_printf(&sbuf, "\nSEGMENT %d:\n\n", segind);
seg = &vm_phys_segs[segind];
sbuf_printf(&sbuf, "start: %#jx\n",
(uintmax_t)seg->start);
sbuf_printf(&sbuf, "end: %#jx\n",
(uintmax_t)seg->end);
sbuf_printf(&sbuf, "free list: %p\n", seg->free_queues);
}
sbuf_finish(&sbuf);
error = SYSCTL_OUT(req, sbuf_data(&sbuf), sbuf_len(&sbuf));
sbuf_delete(&sbuf);
free(cbuf, M_TEMP);
return (error);
}
/*
* Create a physical memory segment.
*/
static void
vm_phys_create_seg(vm_paddr_t start, vm_paddr_t end, int flind)
{
struct vm_phys_seg *seg;
#ifdef VM_PHYSSEG_SPARSE
long pages;
int segind;
pages = 0;
for (segind = 0; segind < vm_phys_nsegs; segind++) {
seg = &vm_phys_segs[segind];
pages += atop(seg->end - seg->start);
}
#endif
KASSERT(vm_phys_nsegs < VM_PHYSSEG_MAX,
("vm_phys_create_seg: increase VM_PHYSSEG_MAX"));
seg = &vm_phys_segs[vm_phys_nsegs++];
seg->start = start;
seg->end = end;
#ifdef VM_PHYSSEG_SPARSE
seg->first_page = &vm_page_array[pages];
#else
seg->first_page = PHYS_TO_VM_PAGE(start);
#endif
seg->free_queues = &vm_phys_free_queues[flind];
}
/*
* Initialize the physical memory allocator.
*/
void
vm_phys_init(void)
{
struct vm_freelist *fl;
int flind, i, oind, pind;
for (i = 0; phys_avail[i + 1] != 0; i += 2) {
#ifdef VM_FREELIST_ISADMA
if (phys_avail[i] < 16777216) {
if (phys_avail[i + 1] > 16777216) {
vm_phys_create_seg(phys_avail[i], 16777216,
VM_FREELIST_ISADMA);
vm_phys_create_seg(16777216, phys_avail[i + 1],
VM_FREELIST_DEFAULT);
} else {
vm_phys_create_seg(phys_avail[i],
phys_avail[i + 1], VM_FREELIST_ISADMA);
}
if (VM_FREELIST_ISADMA >= vm_nfreelists)
vm_nfreelists = VM_FREELIST_ISADMA + 1;
} else
#endif
#ifdef VM_FREELIST_HIGHMEM
if (phys_avail[i + 1] > VM_HIGHMEM_ADDRESS) {
if (phys_avail[i] < VM_HIGHMEM_ADDRESS) {
vm_phys_create_seg(phys_avail[i],
VM_HIGHMEM_ADDRESS, VM_FREELIST_DEFAULT);
vm_phys_create_seg(VM_HIGHMEM_ADDRESS,
phys_avail[i + 1], VM_FREELIST_HIGHMEM);
} else {
vm_phys_create_seg(phys_avail[i],
phys_avail[i + 1], VM_FREELIST_HIGHMEM);
}
if (VM_FREELIST_HIGHMEM >= vm_nfreelists)
vm_nfreelists = VM_FREELIST_HIGHMEM + 1;
} else
#endif
vm_phys_create_seg(phys_avail[i], phys_avail[i + 1],
VM_FREELIST_DEFAULT);
}
for (flind = 0; flind < vm_nfreelists; flind++) {
for (pind = 0; pind < VM_NFREEPOOL; pind++) {
fl = vm_phys_free_queues[flind][pind];
for (oind = 0; oind < VM_NFREEORDER; oind++)
TAILQ_INIT(&fl[oind].pl);
}
}
}
/*
* Split a contiguous, power of two-sized set of physical pages.
*/
static __inline void
vm_phys_split_pages(vm_page_t m, int oind, struct vm_freelist *fl, int order)
{
vm_page_t m_buddy;
while (oind > order) {
oind--;
m_buddy = &m[1 << oind];
KASSERT(m_buddy->order == VM_NFREEORDER,
("vm_phys_split_pages: page %p has unexpected order %d",
m_buddy, m_buddy->order));
m_buddy->order = oind;
TAILQ_INSERT_HEAD(&fl[oind].pl, m_buddy, pageq);
fl[oind].lcnt++;
}
}
/*
* Initialize a physical page and add it to the free lists.
*/
void
vm_phys_add_page(vm_paddr_t pa)
{
vm_page_t m;
cnt.v_page_count++;
m = vm_phys_paddr_to_vm_page(pa);
m->phys_addr = pa;
m->segind = vm_phys_paddr_to_segind(pa);
m->flags = PG_FREE;
KASSERT(m->order == VM_NFREEORDER,
("vm_phys_add_page: page %p has unexpected order %d",
m, m->order));
m->pool = VM_FREEPOOL_DEFAULT;
pmap_page_init(m);
mtx_lock(&vm_page_queue_free_mtx);
Change the management of cached pages (PQ_CACHE) in two fundamental ways: (1) Cached pages are no longer kept in the object's resident page splay tree and memq. Instead, they are kept in a separate per-object splay tree of cached pages. However, access to this new per-object splay tree is synchronized by the _free_ page queues lock, not to be confused with the heavily contended page queues lock. Consequently, a cached page can be reclaimed by vm_page_alloc(9) without acquiring the object's lock or the page queues lock. This solves a problem independently reported by tegge@ and Isilon. Specifically, they observed the page daemon consuming a great deal of CPU time because of pages bouncing back and forth between the cache queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of this problem turned out to be a deadlock avoidance strategy employed when selecting a cached page to reclaim in vm_page_select_cache(). However, the root cause was really that reclaiming a cached page required the acquisition of an object lock while the page queues lock was already held. Thus, this change addresses the problem at its root, by eliminating the need to acquire the object's lock. Moreover, keeping cached pages in the object's primary splay tree and memq was, in effect, optimizing for the uncommon case. Cached pages are reclaimed far, far more often than they are reactivated. Instead, this change makes reclamation cheaper, especially in terms of synchronization overhead, and reactivation more expensive, because reactivated pages will have to be reentered into the object's primary splay tree and memq. (2) Cached pages are now stored alongside free pages in the physical memory allocator's buddy queues, increasing the likelihood that large allocations of contiguous physical memory (i.e., superpages) will succeed. Finally, as a result of this change long-standing restrictions on when and where a cached page can be reclaimed and returned by vm_page_alloc(9) are eliminated. Specifically, calls to vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and return a formerly cached page. Consequently, a call to malloc(9) specifying M_NOWAIT is less likely to fail. Discussed with: many over the course of the summer, including jeff@, Justin Husted @ Isilon, peter@, tegge@ Tested by: an earlier version by kris@ Approved by: re (kensmith)
2007-09-25 06:25:06 +00:00
cnt.v_free_count++;
Eliminate two unused functions: vm_phys_alloc_pages() and vm_phys_free_pages(). Rename vm_phys_alloc_pages_locked() to vm_phys_alloc_pages() and vm_phys_free_pages_locked() to vm_phys_free_pages(). Add comments regarding the need for the free page queues lock to be held by callers to these functions. No functional changes. Approved by: re (hrs)
2007-07-14 21:21:17 +00:00
vm_phys_free_pages(m, 0);
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
mtx_unlock(&vm_page_queue_free_mtx);
}
/*
* Allocate a contiguous, power of two-sized set of physical pages
* from the free lists.
Eliminate two unused functions: vm_phys_alloc_pages() and vm_phys_free_pages(). Rename vm_phys_alloc_pages_locked() to vm_phys_alloc_pages() and vm_phys_free_pages_locked() to vm_phys_free_pages(). Add comments regarding the need for the free page queues lock to be held by callers to these functions. No functional changes. Approved by: re (hrs)
2007-07-14 21:21:17 +00:00
*
* The free page queues must be locked.
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
*/
vm_page_t
Eliminate two unused functions: vm_phys_alloc_pages() and vm_phys_free_pages(). Rename vm_phys_alloc_pages_locked() to vm_phys_alloc_pages() and vm_phys_free_pages_locked() to vm_phys_free_pages(). Add comments regarding the need for the free page queues lock to be held by callers to these functions. No functional changes. Approved by: re (hrs)
2007-07-14 21:21:17 +00:00
vm_phys_alloc_pages(int pool, int order)
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
{
struct vm_freelist *fl;
struct vm_freelist *alt;
int flind, oind, pind;
vm_page_t m;
KASSERT(pool < VM_NFREEPOOL,
Eliminate two unused functions: vm_phys_alloc_pages() and vm_phys_free_pages(). Rename vm_phys_alloc_pages_locked() to vm_phys_alloc_pages() and vm_phys_free_pages_locked() to vm_phys_free_pages(). Add comments regarding the need for the free page queues lock to be held by callers to these functions. No functional changes. Approved by: re (hrs)
2007-07-14 21:21:17 +00:00
("vm_phys_alloc_pages: pool %d is out of range", pool));
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
KASSERT(order < VM_NFREEORDER,
Eliminate two unused functions: vm_phys_alloc_pages() and vm_phys_free_pages(). Rename vm_phys_alloc_pages_locked() to vm_phys_alloc_pages() and vm_phys_free_pages_locked() to vm_phys_free_pages(). Add comments regarding the need for the free page queues lock to be held by callers to these functions. No functional changes. Approved by: re (hrs)
2007-07-14 21:21:17 +00:00
("vm_phys_alloc_pages: order %d is out of range", order));
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
mtx_assert(&vm_page_queue_free_mtx, MA_OWNED);
for (flind = 0; flind < vm_nfreelists; flind++) {
fl = vm_phys_free_queues[flind][pool];
for (oind = order; oind < VM_NFREEORDER; oind++) {
m = TAILQ_FIRST(&fl[oind].pl);
if (m != NULL) {
TAILQ_REMOVE(&fl[oind].pl, m, pageq);
fl[oind].lcnt--;
m->order = VM_NFREEORDER;
vm_phys_split_pages(m, oind, fl, order);
return (m);
}
}
/*
* The given pool was empty. Find the largest
* contiguous, power-of-two-sized set of pages in any
* pool. Transfer these pages to the given pool, and
* use them to satisfy the allocation.
*/
for (oind = VM_NFREEORDER - 1; oind >= order; oind--) {
for (pind = 0; pind < VM_NFREEPOOL; pind++) {
alt = vm_phys_free_queues[flind][pind];
m = TAILQ_FIRST(&alt[oind].pl);
if (m != NULL) {
TAILQ_REMOVE(&alt[oind].pl, m, pageq);
alt[oind].lcnt--;
m->order = VM_NFREEORDER;
vm_phys_set_pool(pool, m, oind);
vm_phys_split_pages(m, oind, fl, order);
return (m);
}
}
}
}
return (NULL);
}
/*
* Allocate physical memory from phys_avail[].
*/
vm_paddr_t
vm_phys_bootstrap_alloc(vm_size_t size, unsigned long alignment)
{
vm_paddr_t pa;
int i;
size = round_page(size);
for (i = 0; phys_avail[i + 1] != 0; i += 2) {
if (phys_avail[i + 1] - phys_avail[i] < size)
continue;
pa = phys_avail[i];
phys_avail[i] += size;
return (pa);
}
panic("vm_phys_bootstrap_alloc");
}
/*
* Find the vm_page corresponding to the given physical address.
*/
vm_page_t
vm_phys_paddr_to_vm_page(vm_paddr_t pa)
{
struct vm_phys_seg *seg;
int segind;
for (segind = 0; segind < vm_phys_nsegs; segind++) {
seg = &vm_phys_segs[segind];
if (pa >= seg->start && pa < seg->end)
return (&seg->first_page[atop(pa - seg->start)]);
}
panic("vm_phys_paddr_to_vm_page: paddr %#jx is not in any segment",
(uintmax_t)pa);
}
/*
* Find the segment containing the given physical address.
*/
static int
vm_phys_paddr_to_segind(vm_paddr_t pa)
{
struct vm_phys_seg *seg;
int segind;
for (segind = 0; segind < vm_phys_nsegs; segind++) {
seg = &vm_phys_segs[segind];
if (pa >= seg->start && pa < seg->end)
return (segind);
}
panic("vm_phys_paddr_to_segind: paddr %#jx is not in any segment" ,
(uintmax_t)pa);
}
/*
* Free a contiguous, power of two-sized set of physical pages.
Eliminate two unused functions: vm_phys_alloc_pages() and vm_phys_free_pages(). Rename vm_phys_alloc_pages_locked() to vm_phys_alloc_pages() and vm_phys_free_pages_locked() to vm_phys_free_pages(). Add comments regarding the need for the free page queues lock to be held by callers to these functions. No functional changes. Approved by: re (hrs)
2007-07-14 21:21:17 +00:00
*
* The free page queues must be locked.
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
*/
void
vm_phys_free_pages(vm_page_t m, int order)
{
struct vm_freelist *fl;
struct vm_phys_seg *seg;
vm_paddr_t pa, pa_buddy;
vm_page_t m_buddy;
KASSERT(m->order == VM_NFREEORDER,
Eliminate two unused functions: vm_phys_alloc_pages() and vm_phys_free_pages(). Rename vm_phys_alloc_pages_locked() to vm_phys_alloc_pages() and vm_phys_free_pages_locked() to vm_phys_free_pages(). Add comments regarding the need for the free page queues lock to be held by callers to these functions. No functional changes. Approved by: re (hrs)
2007-07-14 21:21:17 +00:00
("vm_phys_free_pages: page %p has unexpected order %d",
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
m, m->order));
KASSERT(m->pool < VM_NFREEPOOL,
Eliminate two unused functions: vm_phys_alloc_pages() and vm_phys_free_pages(). Rename vm_phys_alloc_pages_locked() to vm_phys_alloc_pages() and vm_phys_free_pages_locked() to vm_phys_free_pages(). Add comments regarding the need for the free page queues lock to be held by callers to these functions. No functional changes. Approved by: re (hrs)
2007-07-14 21:21:17 +00:00
("vm_phys_free_pages: page %p has unexpected pool %d",
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
m, m->pool));
KASSERT(order < VM_NFREEORDER,
Eliminate two unused functions: vm_phys_alloc_pages() and vm_phys_free_pages(). Rename vm_phys_alloc_pages_locked() to vm_phys_alloc_pages() and vm_phys_free_pages_locked() to vm_phys_free_pages(). Add comments regarding the need for the free page queues lock to be held by callers to these functions. No functional changes. Approved by: re (hrs)
2007-07-14 21:21:17 +00:00
("vm_phys_free_pages: order %d is out of range", order));
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
mtx_assert(&vm_page_queue_free_mtx, MA_OWNED);
pa = VM_PAGE_TO_PHYS(m);
seg = &vm_phys_segs[m->segind];
while (order < VM_NFREEORDER - 1) {
pa_buddy = pa ^ (1 << (PAGE_SHIFT + order));
if (pa_buddy < seg->start ||
pa_buddy >= seg->end)
break;
m_buddy = &seg->first_page[atop(pa_buddy - seg->start)];
if (m_buddy->order != order)
break;
fl = (*seg->free_queues)[m_buddy->pool];
TAILQ_REMOVE(&fl[m_buddy->order].pl, m_buddy, pageq);
fl[m_buddy->order].lcnt--;
m_buddy->order = VM_NFREEORDER;
if (m_buddy->pool != m->pool)
vm_phys_set_pool(m->pool, m_buddy, order);
order++;
pa &= ~((1 << (PAGE_SHIFT + order)) - 1);
m = &seg->first_page[atop(pa - seg->start)];
}
m->order = order;
fl = (*seg->free_queues)[m->pool];
TAILQ_INSERT_TAIL(&fl[order].pl, m, pageq);
fl[order].lcnt++;
}
/*
* Set the pool for a contiguous, power of two-sized set of physical pages.
*/
Change the management of cached pages (PQ_CACHE) in two fundamental ways: (1) Cached pages are no longer kept in the object's resident page splay tree and memq. Instead, they are kept in a separate per-object splay tree of cached pages. However, access to this new per-object splay tree is synchronized by the _free_ page queues lock, not to be confused with the heavily contended page queues lock. Consequently, a cached page can be reclaimed by vm_page_alloc(9) without acquiring the object's lock or the page queues lock. This solves a problem independently reported by tegge@ and Isilon. Specifically, they observed the page daemon consuming a great deal of CPU time because of pages bouncing back and forth between the cache queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of this problem turned out to be a deadlock avoidance strategy employed when selecting a cached page to reclaim in vm_page_select_cache(). However, the root cause was really that reclaiming a cached page required the acquisition of an object lock while the page queues lock was already held. Thus, this change addresses the problem at its root, by eliminating the need to acquire the object's lock. Moreover, keeping cached pages in the object's primary splay tree and memq was, in effect, optimizing for the uncommon case. Cached pages are reclaimed far, far more often than they are reactivated. Instead, this change makes reclamation cheaper, especially in terms of synchronization overhead, and reactivation more expensive, because reactivated pages will have to be reentered into the object's primary splay tree and memq. (2) Cached pages are now stored alongside free pages in the physical memory allocator's buddy queues, increasing the likelihood that large allocations of contiguous physical memory (i.e., superpages) will succeed. Finally, as a result of this change long-standing restrictions on when and where a cached page can be reclaimed and returned by vm_page_alloc(9) are eliminated. Specifically, calls to vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and return a formerly cached page. Consequently, a call to malloc(9) specifying M_NOWAIT is less likely to fail. Discussed with: many over the course of the summer, including jeff@, Justin Husted @ Isilon, peter@, tegge@ Tested by: an earlier version by kris@ Approved by: re (kensmith)
2007-09-25 06:25:06 +00:00
void
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
vm_phys_set_pool(int pool, vm_page_t m, int order)
{
vm_page_t m_tmp;
for (m_tmp = m; m_tmp < &m[1 << order]; m_tmp++)
m_tmp->pool = pool;
}
/*
Update the comment describing vm_phys_unfree_page().
2007-12-21 02:44:31 +00:00
* Search for the given physical page "m" in the free lists. If the search
* succeeds, remove "m" from the free lists and return TRUE. Otherwise, return
* FALSE, indicating that "m" is not in the free lists.
Change the management of cached pages (PQ_CACHE) in two fundamental ways: (1) Cached pages are no longer kept in the object's resident page splay tree and memq. Instead, they are kept in a separate per-object splay tree of cached pages. However, access to this new per-object splay tree is synchronized by the _free_ page queues lock, not to be confused with the heavily contended page queues lock. Consequently, a cached page can be reclaimed by vm_page_alloc(9) without acquiring the object's lock or the page queues lock. This solves a problem independently reported by tegge@ and Isilon. Specifically, they observed the page daemon consuming a great deal of CPU time because of pages bouncing back and forth between the cache queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of this problem turned out to be a deadlock avoidance strategy employed when selecting a cached page to reclaim in vm_page_select_cache(). However, the root cause was really that reclaiming a cached page required the acquisition of an object lock while the page queues lock was already held. Thus, this change addresses the problem at its root, by eliminating the need to acquire the object's lock. Moreover, keeping cached pages in the object's primary splay tree and memq was, in effect, optimizing for the uncommon case. Cached pages are reclaimed far, far more often than they are reactivated. Instead, this change makes reclamation cheaper, especially in terms of synchronization overhead, and reactivation more expensive, because reactivated pages will have to be reentered into the object's primary splay tree and memq. (2) Cached pages are now stored alongside free pages in the physical memory allocator's buddy queues, increasing the likelihood that large allocations of contiguous physical memory (i.e., superpages) will succeed. Finally, as a result of this change long-standing restrictions on when and where a cached page can be reclaimed and returned by vm_page_alloc(9) are eliminated. Specifically, calls to vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and return a formerly cached page. Consequently, a call to malloc(9) specifying M_NOWAIT is less likely to fail. Discussed with: many over the course of the summer, including jeff@, Justin Husted @ Isilon, peter@, tegge@ Tested by: an earlier version by kris@ Approved by: re (kensmith)
2007-09-25 06:25:06 +00:00
*
* The free page queues must be locked.
*/
Modify vm_phys_unfree_page() so that it no longer requires the given page to be in the free lists. Instead, it now returns TRUE if it removed the page from the free lists and FALSE if the page was not in the free lists. This change is required to support superpage reservations. Specifically, once reservations are introduced, a cached page can either be in the free lists or a reservation.
2007-12-20 22:45:54 +00:00
boolean_t
Change the management of cached pages (PQ_CACHE) in two fundamental ways: (1) Cached pages are no longer kept in the object's resident page splay tree and memq. Instead, they are kept in a separate per-object splay tree of cached pages. However, access to this new per-object splay tree is synchronized by the _free_ page queues lock, not to be confused with the heavily contended page queues lock. Consequently, a cached page can be reclaimed by vm_page_alloc(9) without acquiring the object's lock or the page queues lock. This solves a problem independently reported by tegge@ and Isilon. Specifically, they observed the page daemon consuming a great deal of CPU time because of pages bouncing back and forth between the cache queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of this problem turned out to be a deadlock avoidance strategy employed when selecting a cached page to reclaim in vm_page_select_cache(). However, the root cause was really that reclaiming a cached page required the acquisition of an object lock while the page queues lock was already held. Thus, this change addresses the problem at its root, by eliminating the need to acquire the object's lock. Moreover, keeping cached pages in the object's primary splay tree and memq was, in effect, optimizing for the uncommon case. Cached pages are reclaimed far, far more often than they are reactivated. Instead, this change makes reclamation cheaper, especially in terms of synchronization overhead, and reactivation more expensive, because reactivated pages will have to be reentered into the object's primary splay tree and memq. (2) Cached pages are now stored alongside free pages in the physical memory allocator's buddy queues, increasing the likelihood that large allocations of contiguous physical memory (i.e., superpages) will succeed. Finally, as a result of this change long-standing restrictions on when and where a cached page can be reclaimed and returned by vm_page_alloc(9) are eliminated. Specifically, calls to vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and return a formerly cached page. Consequently, a call to malloc(9) specifying M_NOWAIT is less likely to fail. Discussed with: many over the course of the summer, including jeff@, Justin Husted @ Isilon, peter@, tegge@ Tested by: an earlier version by kris@ Approved by: re (kensmith)
2007-09-25 06:25:06 +00:00
vm_phys_unfree_page(vm_page_t m)
{
struct vm_freelist *fl;
struct vm_phys_seg *seg;
vm_paddr_t pa, pa_half;
vm_page_t m_set, m_tmp;
int order;
mtx_assert(&vm_page_queue_free_mtx, MA_OWNED);
/*
* First, find the contiguous, power of two-sized set of free
* physical pages containing the given physical page "m" and
* assign it to "m_set".
*/
seg = &vm_phys_segs[m->segind];
for (m_set = m, order = 0; m_set->order == VM_NFREEORDER &&
Correct one half of a loop continuation condition in vm_phys_unfree_page(). At present, this error is inconsequential; the other half of the loop continuation condition is sufficient to achieve correct execution.
2007-12-19 23:09:45 +00:00
order < VM_NFREEORDER - 1; ) {
Change the management of cached pages (PQ_CACHE) in two fundamental ways: (1) Cached pages are no longer kept in the object's resident page splay tree and memq. Instead, they are kept in a separate per-object splay tree of cached pages. However, access to this new per-object splay tree is synchronized by the _free_ page queues lock, not to be confused with the heavily contended page queues lock. Consequently, a cached page can be reclaimed by vm_page_alloc(9) without acquiring the object's lock or the page queues lock. This solves a problem independently reported by tegge@ and Isilon. Specifically, they observed the page daemon consuming a great deal of CPU time because of pages bouncing back and forth between the cache queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of this problem turned out to be a deadlock avoidance strategy employed when selecting a cached page to reclaim in vm_page_select_cache(). However, the root cause was really that reclaiming a cached page required the acquisition of an object lock while the page queues lock was already held. Thus, this change addresses the problem at its root, by eliminating the need to acquire the object's lock. Moreover, keeping cached pages in the object's primary splay tree and memq was, in effect, optimizing for the uncommon case. Cached pages are reclaimed far, far more often than they are reactivated. Instead, this change makes reclamation cheaper, especially in terms of synchronization overhead, and reactivation more expensive, because reactivated pages will have to be reentered into the object's primary splay tree and memq. (2) Cached pages are now stored alongside free pages in the physical memory allocator's buddy queues, increasing the likelihood that large allocations of contiguous physical memory (i.e., superpages) will succeed. Finally, as a result of this change long-standing restrictions on when and where a cached page can be reclaimed and returned by vm_page_alloc(9) are eliminated. Specifically, calls to vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and return a formerly cached page. Consequently, a call to malloc(9) specifying M_NOWAIT is less likely to fail. Discussed with: many over the course of the summer, including jeff@, Justin Husted @ Isilon, peter@, tegge@ Tested by: an earlier version by kris@ Approved by: re (kensmith)
2007-09-25 06:25:06 +00:00
order++;
pa = m->phys_addr & (~(vm_paddr_t)0 << (PAGE_SHIFT + order));
Eliminate an unnecessary test from vm_phys_unfree_page().
2008-04-05 05:02:53 +00:00
if (pa >= seg->start)
Modify vm_phys_unfree_page() so that it no longer requires the given page to be in the free lists. Instead, it now returns TRUE if it removed the page from the free lists and FALSE if the page was not in the free lists. This change is required to support superpage reservations. Specifically, once reservations are introduced, a cached page can either be in the free lists or a reservation.
2007-12-20 22:45:54 +00:00
m_set = &seg->first_page[atop(pa - seg->start)];
else
return (FALSE);
Change the management of cached pages (PQ_CACHE) in two fundamental ways: (1) Cached pages are no longer kept in the object's resident page splay tree and memq. Instead, they are kept in a separate per-object splay tree of cached pages. However, access to this new per-object splay tree is synchronized by the _free_ page queues lock, not to be confused with the heavily contended page queues lock. Consequently, a cached page can be reclaimed by vm_page_alloc(9) without acquiring the object's lock or the page queues lock. This solves a problem independently reported by tegge@ and Isilon. Specifically, they observed the page daemon consuming a great deal of CPU time because of pages bouncing back and forth between the cache queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of this problem turned out to be a deadlock avoidance strategy employed when selecting a cached page to reclaim in vm_page_select_cache(). However, the root cause was really that reclaiming a cached page required the acquisition of an object lock while the page queues lock was already held. Thus, this change addresses the problem at its root, by eliminating the need to acquire the object's lock. Moreover, keeping cached pages in the object's primary splay tree and memq was, in effect, optimizing for the uncommon case. Cached pages are reclaimed far, far more often than they are reactivated. Instead, this change makes reclamation cheaper, especially in terms of synchronization overhead, and reactivation more expensive, because reactivated pages will have to be reentered into the object's primary splay tree and memq. (2) Cached pages are now stored alongside free pages in the physical memory allocator's buddy queues, increasing the likelihood that large allocations of contiguous physical memory (i.e., superpages) will succeed. Finally, as a result of this change long-standing restrictions on when and where a cached page can be reclaimed and returned by vm_page_alloc(9) are eliminated. Specifically, calls to vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and return a formerly cached page. Consequently, a call to malloc(9) specifying M_NOWAIT is less likely to fail. Discussed with: many over the course of the summer, including jeff@, Justin Husted @ Isilon, peter@, tegge@ Tested by: an earlier version by kris@ Approved by: re (kensmith)
2007-09-25 06:25:06 +00:00
}
Modify vm_phys_unfree_page() so that it no longer requires the given page to be in the free lists. Instead, it now returns TRUE if it removed the page from the free lists and FALSE if the page was not in the free lists. This change is required to support superpage reservations. Specifically, once reservations are introduced, a cached page can either be in the free lists or a reservation.
2007-12-20 22:45:54 +00:00
if (m_set->order < order)
return (FALSE);
if (m_set->order == VM_NFREEORDER)
return (FALSE);
Change the management of cached pages (PQ_CACHE) in two fundamental ways: (1) Cached pages are no longer kept in the object's resident page splay tree and memq. Instead, they are kept in a separate per-object splay tree of cached pages. However, access to this new per-object splay tree is synchronized by the _free_ page queues lock, not to be confused with the heavily contended page queues lock. Consequently, a cached page can be reclaimed by vm_page_alloc(9) without acquiring the object's lock or the page queues lock. This solves a problem independently reported by tegge@ and Isilon. Specifically, they observed the page daemon consuming a great deal of CPU time because of pages bouncing back and forth between the cache queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of this problem turned out to be a deadlock avoidance strategy employed when selecting a cached page to reclaim in vm_page_select_cache(). However, the root cause was really that reclaiming a cached page required the acquisition of an object lock while the page queues lock was already held. Thus, this change addresses the problem at its root, by eliminating the need to acquire the object's lock. Moreover, keeping cached pages in the object's primary splay tree and memq was, in effect, optimizing for the uncommon case. Cached pages are reclaimed far, far more often than they are reactivated. Instead, this change makes reclamation cheaper, especially in terms of synchronization overhead, and reactivation more expensive, because reactivated pages will have to be reentered into the object's primary splay tree and memq. (2) Cached pages are now stored alongside free pages in the physical memory allocator's buddy queues, increasing the likelihood that large allocations of contiguous physical memory (i.e., superpages) will succeed. Finally, as a result of this change long-standing restrictions on when and where a cached page can be reclaimed and returned by vm_page_alloc(9) are eliminated. Specifically, calls to vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and return a formerly cached page. Consequently, a call to malloc(9) specifying M_NOWAIT is less likely to fail. Discussed with: many over the course of the summer, including jeff@, Justin Husted @ Isilon, peter@, tegge@ Tested by: an earlier version by kris@ Approved by: re (kensmith)
2007-09-25 06:25:06 +00:00
KASSERT(m_set->order < VM_NFREEORDER,
("vm_phys_unfree_page: page %p has unexpected order %d",
m_set, m_set->order));
/*
* Next, remove "m_set" from the free lists. Finally, extract
* "m" from "m_set" using an iterative algorithm: While "m_set"
* is larger than a page, shrink "m_set" by returning the half
* of "m_set" that does not contain "m" to the free lists.
*/
fl = (*seg->free_queues)[m_set->pool];
order = m_set->order;
TAILQ_REMOVE(&fl[order].pl, m_set, pageq);
fl[order].lcnt--;
m_set->order = VM_NFREEORDER;
while (order > 0) {
order--;
pa_half = m_set->phys_addr ^ (1 << (PAGE_SHIFT + order));
if (m->phys_addr < pa_half)
m_tmp = &seg->first_page[atop(pa_half - seg->start)];
else {
m_tmp = m_set;
m_set = &seg->first_page[atop(pa_half - seg->start)];
}
m_tmp->order = order;
TAILQ_INSERT_HEAD(&fl[order].pl, m_tmp, pageq);
fl[order].lcnt++;
}
KASSERT(m_set == m, ("vm_phys_unfree_page: fatal inconsistency"));
Modify vm_phys_unfree_page() so that it no longer requires the given page to be in the free lists. Instead, it now returns TRUE if it removed the page from the free lists and FALSE if the page was not in the free lists. This change is required to support superpage reservations. Specifically, once reservations are introduced, a cached page can either be in the free lists or a reservation.
2007-12-20 22:45:54 +00:00
return (TRUE);
Change the management of cached pages (PQ_CACHE) in two fundamental ways: (1) Cached pages are no longer kept in the object's resident page splay tree and memq. Instead, they are kept in a separate per-object splay tree of cached pages. However, access to this new per-object splay tree is synchronized by the _free_ page queues lock, not to be confused with the heavily contended page queues lock. Consequently, a cached page can be reclaimed by vm_page_alloc(9) without acquiring the object's lock or the page queues lock. This solves a problem independently reported by tegge@ and Isilon. Specifically, they observed the page daemon consuming a great deal of CPU time because of pages bouncing back and forth between the cache queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of this problem turned out to be a deadlock avoidance strategy employed when selecting a cached page to reclaim in vm_page_select_cache(). However, the root cause was really that reclaiming a cached page required the acquisition of an object lock while the page queues lock was already held. Thus, this change addresses the problem at its root, by eliminating the need to acquire the object's lock. Moreover, keeping cached pages in the object's primary splay tree and memq was, in effect, optimizing for the uncommon case. Cached pages are reclaimed far, far more often than they are reactivated. Instead, this change makes reclamation cheaper, especially in terms of synchronization overhead, and reactivation more expensive, because reactivated pages will have to be reentered into the object's primary splay tree and memq. (2) Cached pages are now stored alongside free pages in the physical memory allocator's buddy queues, increasing the likelihood that large allocations of contiguous physical memory (i.e., superpages) will succeed. Finally, as a result of this change long-standing restrictions on when and where a cached page can be reclaimed and returned by vm_page_alloc(9) are eliminated. Specifically, calls to vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and return a formerly cached page. Consequently, a call to malloc(9) specifying M_NOWAIT is less likely to fail. Discussed with: many over the course of the summer, including jeff@, Justin Husted @ Isilon, peter@, tegge@ Tested by: an earlier version by kris@ Approved by: re (kensmith)
2007-09-25 06:25:06 +00:00
}
/*
* Try to zero one physical page. Used by an idle priority thread.
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
*/
boolean_t
vm_phys_zero_pages_idle(void)
{
Change the management of cached pages (PQ_CACHE) in two fundamental ways: (1) Cached pages are no longer kept in the object's resident page splay tree and memq. Instead, they are kept in a separate per-object splay tree of cached pages. However, access to this new per-object splay tree is synchronized by the _free_ page queues lock, not to be confused with the heavily contended page queues lock. Consequently, a cached page can be reclaimed by vm_page_alloc(9) without acquiring the object's lock or the page queues lock. This solves a problem independently reported by tegge@ and Isilon. Specifically, they observed the page daemon consuming a great deal of CPU time because of pages bouncing back and forth between the cache queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of this problem turned out to be a deadlock avoidance strategy employed when selecting a cached page to reclaim in vm_page_select_cache(). However, the root cause was really that reclaiming a cached page required the acquisition of an object lock while the page queues lock was already held. Thus, this change addresses the problem at its root, by eliminating the need to acquire the object's lock. Moreover, keeping cached pages in the object's primary splay tree and memq was, in effect, optimizing for the uncommon case. Cached pages are reclaimed far, far more often than they are reactivated. Instead, this change makes reclamation cheaper, especially in terms of synchronization overhead, and reactivation more expensive, because reactivated pages will have to be reentered into the object's primary splay tree and memq. (2) Cached pages are now stored alongside free pages in the physical memory allocator's buddy queues, increasing the likelihood that large allocations of contiguous physical memory (i.e., superpages) will succeed. Finally, as a result of this change long-standing restrictions on when and where a cached page can be reclaimed and returned by vm_page_alloc(9) are eliminated. Specifically, calls to vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and return a formerly cached page. Consequently, a call to malloc(9) specifying M_NOWAIT is less likely to fail. Discussed with: many over the course of the summer, including jeff@, Justin Husted @ Isilon, peter@, tegge@ Tested by: an earlier version by kris@ Approved by: re (kensmith)
2007-09-25 06:25:06 +00:00
static struct vm_freelist *fl = vm_phys_free_queues[0][0];
static int flind, oind, pind;
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
vm_page_t m, m_tmp;
mtx_assert(&vm_page_queue_free_mtx, MA_OWNED);
Change the management of cached pages (PQ_CACHE) in two fundamental ways: (1) Cached pages are no longer kept in the object's resident page splay tree and memq. Instead, they are kept in a separate per-object splay tree of cached pages. However, access to this new per-object splay tree is synchronized by the _free_ page queues lock, not to be confused with the heavily contended page queues lock. Consequently, a cached page can be reclaimed by vm_page_alloc(9) without acquiring the object's lock or the page queues lock. This solves a problem independently reported by tegge@ and Isilon. Specifically, they observed the page daemon consuming a great deal of CPU time because of pages bouncing back and forth between the cache queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of this problem turned out to be a deadlock avoidance strategy employed when selecting a cached page to reclaim in vm_page_select_cache(). However, the root cause was really that reclaiming a cached page required the acquisition of an object lock while the page queues lock was already held. Thus, this change addresses the problem at its root, by eliminating the need to acquire the object's lock. Moreover, keeping cached pages in the object's primary splay tree and memq was, in effect, optimizing for the uncommon case. Cached pages are reclaimed far, far more often than they are reactivated. Instead, this change makes reclamation cheaper, especially in terms of synchronization overhead, and reactivation more expensive, because reactivated pages will have to be reentered into the object's primary splay tree and memq. (2) Cached pages are now stored alongside free pages in the physical memory allocator's buddy queues, increasing the likelihood that large allocations of contiguous physical memory (i.e., superpages) will succeed. Finally, as a result of this change long-standing restrictions on when and where a cached page can be reclaimed and returned by vm_page_alloc(9) are eliminated. Specifically, calls to vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and return a formerly cached page. Consequently, a call to malloc(9) specifying M_NOWAIT is less likely to fail. Discussed with: many over the course of the summer, including jeff@, Justin Husted @ Isilon, peter@, tegge@ Tested by: an earlier version by kris@ Approved by: re (kensmith)
2007-09-25 06:25:06 +00:00
for (;;) {
TAILQ_FOREACH_REVERSE(m, &fl[oind].pl, pglist, pageq) {
for (m_tmp = m; m_tmp < &m[1 << oind]; m_tmp++) {
if ((m_tmp->flags & (PG_CACHED | PG_ZERO)) == 0) {
vm_phys_unfree_page(m_tmp);
cnt.v_free_count--;
mtx_unlock(&vm_page_queue_free_mtx);
pmap_zero_page_idle(m_tmp);
m_tmp->flags |= PG_ZERO;
mtx_lock(&vm_page_queue_free_mtx);
cnt.v_free_count++;
vm_phys_free_pages(m_tmp, 0);
vm_page_zero_count++;
cnt_prezero++;
return (TRUE);
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
}
}
}
Change the management of cached pages (PQ_CACHE) in two fundamental ways: (1) Cached pages are no longer kept in the object's resident page splay tree and memq. Instead, they are kept in a separate per-object splay tree of cached pages. However, access to this new per-object splay tree is synchronized by the _free_ page queues lock, not to be confused with the heavily contended page queues lock. Consequently, a cached page can be reclaimed by vm_page_alloc(9) without acquiring the object's lock or the page queues lock. This solves a problem independently reported by tegge@ and Isilon. Specifically, they observed the page daemon consuming a great deal of CPU time because of pages bouncing back and forth between the cache queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of this problem turned out to be a deadlock avoidance strategy employed when selecting a cached page to reclaim in vm_page_select_cache(). However, the root cause was really that reclaiming a cached page required the acquisition of an object lock while the page queues lock was already held. Thus, this change addresses the problem at its root, by eliminating the need to acquire the object's lock. Moreover, keeping cached pages in the object's primary splay tree and memq was, in effect, optimizing for the uncommon case. Cached pages are reclaimed far, far more often than they are reactivated. Instead, this change makes reclamation cheaper, especially in terms of synchronization overhead, and reactivation more expensive, because reactivated pages will have to be reentered into the object's primary splay tree and memq. (2) Cached pages are now stored alongside free pages in the physical memory allocator's buddy queues, increasing the likelihood that large allocations of contiguous physical memory (i.e., superpages) will succeed. Finally, as a result of this change long-standing restrictions on when and where a cached page can be reclaimed and returned by vm_page_alloc(9) are eliminated. Specifically, calls to vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and return a formerly cached page. Consequently, a call to malloc(9) specifying M_NOWAIT is less likely to fail. Discussed with: many over the course of the summer, including jeff@, Justin Husted @ Isilon, peter@, tegge@ Tested by: an earlier version by kris@ Approved by: re (kensmith)
2007-09-25 06:25:06 +00:00
oind++;
if (oind == VM_NFREEORDER) {
oind = 0;
pind++;
if (pind == VM_NFREEPOOL) {
pind = 0;
flind++;
if (flind == vm_nfreelists)
flind = 0;
}
fl = vm_phys_free_queues[flind][pind];
}
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
}
}
/*
Update a comment.
2007-06-16 05:25:53 +00:00
* Allocate a contiguous set of physical pages of the given size
* "npages" from the free lists. All of the physical pages must be at
* or above the given physical address "low" and below the given
* physical address "high". The given value "alignment" determines the
* alignment of the first physical page in the set. If the given value
* "boundary" is non-zero, then the set of physical pages cannot cross
* any physical address boundary that is a multiple of that value. Both
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
* "alignment" and "boundary" must be a power of two.
*/
vm_page_t
vm_phys_alloc_contig(unsigned long npages, vm_paddr_t low, vm_paddr_t high,
unsigned long alignment, unsigned long boundary)
{
struct vm_freelist *fl;
struct vm_phys_seg *seg;
Change the management of cached pages (PQ_CACHE) in two fundamental ways: (1) Cached pages are no longer kept in the object's resident page splay tree and memq. Instead, they are kept in a separate per-object splay tree of cached pages. However, access to this new per-object splay tree is synchronized by the _free_ page queues lock, not to be confused with the heavily contended page queues lock. Consequently, a cached page can be reclaimed by vm_page_alloc(9) without acquiring the object's lock or the page queues lock. This solves a problem independently reported by tegge@ and Isilon. Specifically, they observed the page daemon consuming a great deal of CPU time because of pages bouncing back and forth between the cache queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of this problem turned out to be a deadlock avoidance strategy employed when selecting a cached page to reclaim in vm_page_select_cache(). However, the root cause was really that reclaiming a cached page required the acquisition of an object lock while the page queues lock was already held. Thus, this change addresses the problem at its root, by eliminating the need to acquire the object's lock. Moreover, keeping cached pages in the object's primary splay tree and memq was, in effect, optimizing for the uncommon case. Cached pages are reclaimed far, far more often than they are reactivated. Instead, this change makes reclamation cheaper, especially in terms of synchronization overhead, and reactivation more expensive, because reactivated pages will have to be reentered into the object's primary splay tree and memq. (2) Cached pages are now stored alongside free pages in the physical memory allocator's buddy queues, increasing the likelihood that large allocations of contiguous physical memory (i.e., superpages) will succeed. Finally, as a result of this change long-standing restrictions on when and where a cached page can be reclaimed and returned by vm_page_alloc(9) are eliminated. Specifically, calls to vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and return a formerly cached page. Consequently, a call to malloc(9) specifying M_NOWAIT is less likely to fail. Discussed with: many over the course of the summer, including jeff@, Justin Husted @ Isilon, peter@, tegge@ Tested by: an earlier version by kris@ Approved by: re (kensmith)
2007-09-25 06:25:06 +00:00
vm_object_t m_object;
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
vm_paddr_t pa, pa_last, size;
vm_page_t m, m_ret;
int flind, i, oind, order, pind;
size = npages << PAGE_SHIFT;
KASSERT(size != 0,
("vm_phys_alloc_contig: size must not be 0"));
KASSERT((alignment & (alignment - 1)) == 0,
("vm_phys_alloc_contig: alignment must be a power of 2"));
KASSERT((boundary & (boundary - 1)) == 0,
("vm_phys_alloc_contig: boundary must be a power of 2"));
/* Compute the queue that is the best fit for npages. */
for (order = 0; (1 << order) < npages; order++);
mtx_lock(&vm_page_queue_free_mtx);
for (flind = 0; flind < vm_nfreelists; flind++) {
for (oind = min(order, VM_NFREEORDER - 1); oind < VM_NFREEORDER; oind++) {
for (pind = 0; pind < VM_NFREEPOOL; pind++) {
fl = vm_phys_free_queues[flind][pind];
TAILQ_FOREACH(m_ret, &fl[oind].pl, pageq) {
/*
* A free list may contain physical pages
* from one or more segments.
*/
seg = &vm_phys_segs[m_ret->segind];
if (seg->start > high ||
low >= seg->end)
continue;
/*
* Is the size of this allocation request
* larger than the largest block size?
*/
if (order >= VM_NFREEORDER) {
/*
* Determine if a sufficient number
* of subsequent blocks to satisfy
* the allocation request are free.
*/
pa = VM_PAGE_TO_PHYS(m_ret);
pa_last = pa + size;
for (;;) {
pa += 1 << (PAGE_SHIFT + VM_NFREEORDER - 1);
if (pa >= pa_last)
break;
if (pa < seg->start ||
pa >= seg->end)
break;
m = &seg->first_page[atop(pa - seg->start)];
if (m->order != VM_NFREEORDER - 1)
break;
}
/* If not, continue to the next block. */
if (pa < pa_last)
continue;
}
/*
* Determine if the blocks are within the given range,
* satisfy the given alignment, and do not cross the
* given boundary.
*/
pa = VM_PAGE_TO_PHYS(m_ret);
if (pa >= low &&
pa + size <= high &&
(pa & (alignment - 1)) == 0 &&
((pa ^ (pa + size - 1)) & ~(boundary - 1)) == 0)
goto done;
}
}
}
}
mtx_unlock(&vm_page_queue_free_mtx);
return (NULL);
done:
for (m = m_ret; m < &m_ret[npages]; m = &m[1 << oind]) {
fl = (*seg->free_queues)[m->pool];
TAILQ_REMOVE(&fl[m->order].pl, m, pageq);
fl[m->order].lcnt--;
m->order = VM_NFREEORDER;
}
if (m_ret->pool != VM_FREEPOOL_DEFAULT)
vm_phys_set_pool(VM_FREEPOOL_DEFAULT, m_ret, oind);
fl = (*seg->free_queues)[m_ret->pool];
vm_phys_split_pages(m_ret, oind, fl, order);
for (i = 0; i < npages; i++) {
m = &m_ret[i];
KASSERT(m->queue == PQ_NONE,
("vm_phys_alloc_contig: page %p has unexpected queue %d",
m, m->queue));
Change the management of cached pages (PQ_CACHE) in two fundamental ways: (1) Cached pages are no longer kept in the object's resident page splay tree and memq. Instead, they are kept in a separate per-object splay tree of cached pages. However, access to this new per-object splay tree is synchronized by the _free_ page queues lock, not to be confused with the heavily contended page queues lock. Consequently, a cached page can be reclaimed by vm_page_alloc(9) without acquiring the object's lock or the page queues lock. This solves a problem independently reported by tegge@ and Isilon. Specifically, they observed the page daemon consuming a great deal of CPU time because of pages bouncing back and forth between the cache queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of this problem turned out to be a deadlock avoidance strategy employed when selecting a cached page to reclaim in vm_page_select_cache(). However, the root cause was really that reclaiming a cached page required the acquisition of an object lock while the page queues lock was already held. Thus, this change addresses the problem at its root, by eliminating the need to acquire the object's lock. Moreover, keeping cached pages in the object's primary splay tree and memq was, in effect, optimizing for the uncommon case. Cached pages are reclaimed far, far more often than they are reactivated. Instead, this change makes reclamation cheaper, especially in terms of synchronization overhead, and reactivation more expensive, because reactivated pages will have to be reentered into the object's primary splay tree and memq. (2) Cached pages are now stored alongside free pages in the physical memory allocator's buddy queues, increasing the likelihood that large allocations of contiguous physical memory (i.e., superpages) will succeed. Finally, as a result of this change long-standing restrictions on when and where a cached page can be reclaimed and returned by vm_page_alloc(9) are eliminated. Specifically, calls to vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and return a formerly cached page. Consequently, a call to malloc(9) specifying M_NOWAIT is less likely to fail. Discussed with: many over the course of the summer, including jeff@, Justin Husted @ Isilon, peter@, tegge@ Tested by: an earlier version by kris@ Approved by: re (kensmith)
2007-09-25 06:25:06 +00:00
m_object = m->object;
if ((m->flags & PG_CACHED) != 0)
vm_page_cache_remove(m);
else {
KASSERT(VM_PAGE_IS_FREE(m),
("vm_phys_alloc_contig: page %p is not free", m));
cnt.v_free_count--;
}
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
m->valid = VM_PAGE_BITS_ALL;
if (m->flags & PG_ZERO)
vm_page_zero_count--;
/* Don't clear the PG_ZERO flag; we'll need it later. */
m->flags = PG_UNMANAGED | (m->flags & PG_ZERO);
m->oflags = 0;
KASSERT(m->dirty == 0,
("vm_phys_alloc_contig: page %p was dirty", m));
m->wire_count = 0;
m->busy = 0;
Change the management of cached pages (PQ_CACHE) in two fundamental ways: (1) Cached pages are no longer kept in the object's resident page splay tree and memq. Instead, they are kept in a separate per-object splay tree of cached pages. However, access to this new per-object splay tree is synchronized by the _free_ page queues lock, not to be confused with the heavily contended page queues lock. Consequently, a cached page can be reclaimed by vm_page_alloc(9) without acquiring the object's lock or the page queues lock. This solves a problem independently reported by tegge@ and Isilon. Specifically, they observed the page daemon consuming a great deal of CPU time because of pages bouncing back and forth between the cache queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE). The source of this problem turned out to be a deadlock avoidance strategy employed when selecting a cached page to reclaim in vm_page_select_cache(). However, the root cause was really that reclaiming a cached page required the acquisition of an object lock while the page queues lock was already held. Thus, this change addresses the problem at its root, by eliminating the need to acquire the object's lock. Moreover, keeping cached pages in the object's primary splay tree and memq was, in effect, optimizing for the uncommon case. Cached pages are reclaimed far, far more often than they are reactivated. Instead, this change makes reclamation cheaper, especially in terms of synchronization overhead, and reactivation more expensive, because reactivated pages will have to be reentered into the object's primary splay tree and memq. (2) Cached pages are now stored alongside free pages in the physical memory allocator's buddy queues, increasing the likelihood that large allocations of contiguous physical memory (i.e., superpages) will succeed. Finally, as a result of this change long-standing restrictions on when and where a cached page can be reclaimed and returned by vm_page_alloc(9) are eliminated. Specifically, calls to vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and return a formerly cached page. Consequently, a call to malloc(9) specifying M_NOWAIT is less likely to fail. Discussed with: many over the course of the summer, including jeff@, Justin Husted @ Isilon, peter@, tegge@ Tested by: an earlier version by kris@ Approved by: re (kensmith)
2007-09-25 06:25:06 +00:00
if (m_object != NULL &&
m_object->type == OBJT_VNODE &&
m_object->cache == NULL) {
mtx_unlock(&vm_page_queue_free_mtx);
vdrop(m_object->handle);
mtx_lock(&vm_page_queue_free_mtx);
}
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
}
for (; i < roundup2(npages, 1 << imin(oind, order)); i++) {
m = &m_ret[i];
KASSERT(m->order == VM_NFREEORDER,
("vm_phys_alloc_contig: page %p has unexpected order %d",
m, m->order));
Eliminate two unused functions: vm_phys_alloc_pages() and vm_phys_free_pages(). Rename vm_phys_alloc_pages_locked() to vm_phys_alloc_pages() and vm_phys_free_pages_locked() to vm_phys_free_pages(). Add comments regarding the need for the free page queues lock to be held by callers to these functions. No functional changes. Approved by: re (hrs)
2007-07-14 21:21:17 +00:00
vm_phys_free_pages(m, 0);
Add a new physical memory allocator. However, do not yet connect it to the build. This allocator uses a binary buddy system with a twist. First and foremost, this allocator is required to support the implementation of superpages. As a side effect, it enables a more robust implementation of contigmalloc(9). Moreover, this reimplementation of contigmalloc(9) eliminates the acquisition of Giant by contigmalloc(..., M_NOWAIT, ...). The twist is that this allocator tries to reduce the number of TLB misses incurred by accesses through a direct map to small, UMA-managed objects and page table pages. Roughly speaking, the physical pages that are allocated for such purposes are clustered together in the physical address space. The performance benefits vary. In the most extreme case, a uniprocessor kernel running on an Opteron, I measured an 18% reduction in system time during a buildworld. This allocator does not implement page coloring. The reason is that superpages have much the same effect. The contiguous physical memory allocation necessary for a superpage is inherently colored. Finally, the one caveat is that this allocator does not effectively support prezeroed pages. I hope this is temporary. On i386, this is a slight pessimization. However, on amd64, the beneficial effects of the direct-map optimization outweigh the ill effects. I speculate that this is true in general of machines with a direct map. Approved by: re
2007-06-10 00:49:16 +00:00
}
mtx_unlock(&vm_page_queue_free_mtx);
return (m_ret);
}
#ifdef DDB
/*
* Show the number of physical pages in each of the free lists.
*/
DB_SHOW_COMMAND(freepages, db_show_freepages)
{
struct vm_freelist *fl;
int flind, oind, pind;
for (flind = 0; flind < vm_nfreelists; flind++) {
db_printf("FREE LIST %d:\n"
"\n ORDER (SIZE) | NUMBER"
"\n ", flind);
for (pind = 0; pind < VM_NFREEPOOL; pind++)
db_printf(" | POOL %d", pind);
db_printf("\n-- ");
for (pind = 0; pind < VM_NFREEPOOL; pind++)
db_printf("-- -- ");
db_printf("--\n");
for (oind = VM_NFREEORDER - 1; oind >= 0; oind--) {
db_printf(" %2.2d (%6.6dK)", oind,
1 << (PAGE_SHIFT - 10 + oind));
for (pind = 0; pind < VM_NFREEPOOL; pind++) {
fl = vm_phys_free_queues[flind][pind];
db_printf(" | %6.6d", fl[oind].lcnt);
}
db_printf("\n");
}
db_printf("\n");
}
}
#endif
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