freebsd-skq/sys/vm/vm_glue.c
kib c7d26e1c75 Fix a LOR between vnode locks and allproc_lock.
There is an order between covered vnode lock and allproc_lock, which
is established by calling mountcheckdirs() while owning the covered
vnode lock. mountcheckdirs() iterates over the processes, protected by
allproc_lock.  This order is needed and seems to be not avoidable.

On the other hand, various VM daemons also need to iterate over all
processes, and they lock and unlock user maps.  Since unlock of the
user map may trigger processing of the deferred map entries, it causes
vnode locking to occur.  Or, when vmspace is freed, dropping references
on the vnode-backed object also lock vnodes.  We get reverted order
comparing with the mount/unmount order.

For VM daemons, there is no need to own allproc_lock while we operate
on vmspaces. If the process is held, it serves as the marker for
allproc list, which allows to continue the iteration.

Add _PHOLD_LITE() macro, similar to _PHOLD(), but not causing swap-in
of the kernel stacks.  It is used instead of _PHOLD() in vm code,
since e.g. calling faultin() in OOM conditions only exaggerates the
problem.

Modernize comment describing PHOLD.

Reported by:	lists@yamagi.org
Tested by:	pho (previous version)
Reviewed by:	jhb
Sponsored by:	The FreeBSD Foundation
MFC after:	3 week
Approved by:	re (gjb)
Differential revision:	https://reviews.freebsd.org/D6679
2016-06-22 20:15:37 +00:00

1103 lines
26 KiB
C

/*-
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* The Mach Operating System project at Carnegie-Mellon University.
*
* 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.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
*
* from: @(#)vm_glue.c 8.6 (Berkeley) 1/5/94
*
*
* Copyright (c) 1987, 1990 Carnegie-Mellon University.
* All rights reserved.
*
* Permission to use, copy, modify and distribute this software and
* its documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_vm.h"
#include "opt_kstack_pages.h"
#include "opt_kstack_max_pages.h"
#include "opt_kstack_usage_prof.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/racct.h>
#include <sys/resourcevar.h>
#include <sys/rwlock.h>
#include <sys/sched.h>
#include <sys/sf_buf.h>
#include <sys/shm.h>
#include <sys/vmmeter.h>
#include <sys/vmem.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/_kstack_cache.h>
#include <sys/eventhandler.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/unistd.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
#include <vm/vm_object.h>
#include <vm/vm_kern.h>
#include <vm/vm_extern.h>
#include <vm/vm_pager.h>
#include <vm/swap_pager.h>
#include <machine/cpu.h>
#ifndef NO_SWAPPING
static int swapout(struct proc *);
static void swapclear(struct proc *);
static void vm_thread_swapin(struct thread *td);
static void vm_thread_swapout(struct thread *td);
#endif
/*
* MPSAFE
*
* WARNING! This code calls vm_map_check_protection() which only checks
* the associated vm_map_entry range. It does not determine whether the
* contents of the memory is actually readable or writable. In most cases
* just checking the vm_map_entry is sufficient within the kernel's address
* space.
*/
int
kernacc(addr, len, rw)
void *addr;
int len, rw;
{
boolean_t rv;
vm_offset_t saddr, eaddr;
vm_prot_t prot;
KASSERT((rw & ~VM_PROT_ALL) == 0,
("illegal ``rw'' argument to kernacc (%x)\n", rw));
if ((vm_offset_t)addr + len > kernel_map->max_offset ||
(vm_offset_t)addr + len < (vm_offset_t)addr)
return (FALSE);
prot = rw;
saddr = trunc_page((vm_offset_t)addr);
eaddr = round_page((vm_offset_t)addr + len);
vm_map_lock_read(kernel_map);
rv = vm_map_check_protection(kernel_map, saddr, eaddr, prot);
vm_map_unlock_read(kernel_map);
return (rv == TRUE);
}
/*
* MPSAFE
*
* WARNING! This code calls vm_map_check_protection() which only checks
* the associated vm_map_entry range. It does not determine whether the
* contents of the memory is actually readable or writable. vmapbuf(),
* vm_fault_quick(), or copyin()/copout()/su*()/fu*() functions should be
* used in conjunction with this call.
*/
int
useracc(addr, len, rw)
void *addr;
int len, rw;
{
boolean_t rv;
vm_prot_t prot;
vm_map_t map;
KASSERT((rw & ~VM_PROT_ALL) == 0,
("illegal ``rw'' argument to useracc (%x)\n", rw));
prot = rw;
map = &curproc->p_vmspace->vm_map;
if ((vm_offset_t)addr + len > vm_map_max(map) ||
(vm_offset_t)addr + len < (vm_offset_t)addr) {
return (FALSE);
}
vm_map_lock_read(map);
rv = vm_map_check_protection(map, trunc_page((vm_offset_t)addr),
round_page((vm_offset_t)addr + len), prot);
vm_map_unlock_read(map);
return (rv == TRUE);
}
int
vslock(void *addr, size_t len)
{
vm_offset_t end, last, start;
vm_size_t npages;
int error;
last = (vm_offset_t)addr + len;
start = trunc_page((vm_offset_t)addr);
end = round_page(last);
if (last < (vm_offset_t)addr || end < (vm_offset_t)addr)
return (EINVAL);
npages = atop(end - start);
if (npages > vm_page_max_wired)
return (ENOMEM);
#if 0
/*
* XXX - not yet
*
* The limit for transient usage of wired pages should be
* larger than for "permanent" wired pages (mlock()).
*
* Also, the sysctl code, which is the only present user
* of vslock(), does a hard loop on EAGAIN.
*/
if (npages + vm_cnt.v_wire_count > vm_page_max_wired)
return (EAGAIN);
#endif
error = vm_map_wire(&curproc->p_vmspace->vm_map, start, end,
VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES);
/*
* Return EFAULT on error to match copy{in,out}() behaviour
* rather than returning ENOMEM like mlock() would.
*/
return (error == KERN_SUCCESS ? 0 : EFAULT);
}
void
vsunlock(void *addr, size_t len)
{
/* Rely on the parameter sanity checks performed by vslock(). */
(void)vm_map_unwire(&curproc->p_vmspace->vm_map,
trunc_page((vm_offset_t)addr), round_page((vm_offset_t)addr + len),
VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES);
}
/*
* Pin the page contained within the given object at the given offset. If the
* page is not resident, allocate and load it using the given object's pager.
* Return the pinned page if successful; otherwise, return NULL.
*/
static vm_page_t
vm_imgact_hold_page(vm_object_t object, vm_ooffset_t offset)
{
vm_page_t m;
vm_pindex_t pindex;
int rv;
VM_OBJECT_WLOCK(object);
pindex = OFF_TO_IDX(offset);
m = vm_page_grab(object, pindex, VM_ALLOC_NORMAL);
if (m->valid != VM_PAGE_BITS_ALL) {
rv = vm_pager_get_pages(object, &m, 1, NULL, NULL);
if (rv != VM_PAGER_OK) {
vm_page_lock(m);
vm_page_free(m);
vm_page_unlock(m);
m = NULL;
goto out;
}
}
vm_page_xunbusy(m);
vm_page_lock(m);
vm_page_hold(m);
vm_page_activate(m);
vm_page_unlock(m);
out:
VM_OBJECT_WUNLOCK(object);
return (m);
}
/*
* Return a CPU private mapping to the page at the given offset within the
* given object. The page is pinned before it is mapped.
*/
struct sf_buf *
vm_imgact_map_page(vm_object_t object, vm_ooffset_t offset)
{
vm_page_t m;
m = vm_imgact_hold_page(object, offset);
if (m == NULL)
return (NULL);
sched_pin();
return (sf_buf_alloc(m, SFB_CPUPRIVATE));
}
/*
* Destroy the given CPU private mapping and unpin the page that it mapped.
*/
void
vm_imgact_unmap_page(struct sf_buf *sf)
{
vm_page_t m;
m = sf_buf_page(sf);
sf_buf_free(sf);
sched_unpin();
vm_page_lock(m);
vm_page_unhold(m);
vm_page_unlock(m);
}
void
vm_sync_icache(vm_map_t map, vm_offset_t va, vm_offset_t sz)
{
pmap_sync_icache(map->pmap, va, sz);
}
struct kstack_cache_entry *kstack_cache;
static int kstack_cache_size = 128;
static int kstacks;
static struct mtx kstack_cache_mtx;
MTX_SYSINIT(kstack_cache, &kstack_cache_mtx, "kstkch", MTX_DEF);
SYSCTL_INT(_vm, OID_AUTO, kstack_cache_size, CTLFLAG_RW, &kstack_cache_size, 0,
"");
SYSCTL_INT(_vm, OID_AUTO, kstacks, CTLFLAG_RD, &kstacks, 0,
"");
#ifndef KSTACK_MAX_PAGES
#define KSTACK_MAX_PAGES 32
#endif
/*
* Create the kernel stack (including pcb for i386) for a new thread.
* This routine directly affects the fork perf for a process and
* create performance for a thread.
*/
int
vm_thread_new(struct thread *td, int pages)
{
vm_object_t ksobj;
vm_offset_t ks;
vm_page_t m, ma[KSTACK_MAX_PAGES];
struct kstack_cache_entry *ks_ce;
int i;
/* Bounds check */
if (pages <= 1)
pages = kstack_pages;
else if (pages > KSTACK_MAX_PAGES)
pages = KSTACK_MAX_PAGES;
if (pages == kstack_pages) {
mtx_lock(&kstack_cache_mtx);
if (kstack_cache != NULL) {
ks_ce = kstack_cache;
kstack_cache = ks_ce->next_ks_entry;
mtx_unlock(&kstack_cache_mtx);
td->td_kstack_obj = ks_ce->ksobj;
td->td_kstack = (vm_offset_t)ks_ce;
td->td_kstack_pages = kstack_pages;
return (1);
}
mtx_unlock(&kstack_cache_mtx);
}
/*
* Allocate an object for the kstack.
*/
ksobj = vm_object_allocate(OBJT_DEFAULT, pages);
/*
* Get a kernel virtual address for this thread's kstack.
*/
#if defined(__mips__)
/*
* We need to align the kstack's mapped address to fit within
* a single TLB entry.
*/
if (vmem_xalloc(kernel_arena, (pages + KSTACK_GUARD_PAGES) * PAGE_SIZE,
PAGE_SIZE * 2, 0, 0, VMEM_ADDR_MIN, VMEM_ADDR_MAX,
M_BESTFIT | M_NOWAIT, &ks)) {
ks = 0;
}
#else
ks = kva_alloc((pages + KSTACK_GUARD_PAGES) * PAGE_SIZE);
#endif
if (ks == 0) {
printf("vm_thread_new: kstack allocation failed\n");
vm_object_deallocate(ksobj);
return (0);
}
atomic_add_int(&kstacks, 1);
if (KSTACK_GUARD_PAGES != 0) {
pmap_qremove(ks, KSTACK_GUARD_PAGES);
ks += KSTACK_GUARD_PAGES * PAGE_SIZE;
}
td->td_kstack_obj = ksobj;
td->td_kstack = ks;
/*
* Knowing the number of pages allocated is useful when you
* want to deallocate them.
*/
td->td_kstack_pages = pages;
/*
* For the length of the stack, link in a real page of ram for each
* page of stack.
*/
VM_OBJECT_WLOCK(ksobj);
for (i = 0; i < pages; i++) {
/*
* Get a kernel stack page.
*/
m = vm_page_grab(ksobj, i, VM_ALLOC_NOBUSY |
VM_ALLOC_NORMAL | VM_ALLOC_WIRED);
ma[i] = m;
m->valid = VM_PAGE_BITS_ALL;
}
VM_OBJECT_WUNLOCK(ksobj);
pmap_qenter(ks, ma, pages);
return (1);
}
static void
vm_thread_stack_dispose(vm_object_t ksobj, vm_offset_t ks, int pages)
{
vm_page_t m;
int i;
atomic_add_int(&kstacks, -1);
pmap_qremove(ks, pages);
VM_OBJECT_WLOCK(ksobj);
for (i = 0; i < pages; i++) {
m = vm_page_lookup(ksobj, i);
if (m == NULL)
panic("vm_thread_dispose: kstack already missing?");
vm_page_lock(m);
vm_page_unwire(m, PQ_NONE);
vm_page_free(m);
vm_page_unlock(m);
}
VM_OBJECT_WUNLOCK(ksobj);
vm_object_deallocate(ksobj);
kva_free(ks - (KSTACK_GUARD_PAGES * PAGE_SIZE),
(pages + KSTACK_GUARD_PAGES) * PAGE_SIZE);
}
/*
* Dispose of a thread's kernel stack.
*/
void
vm_thread_dispose(struct thread *td)
{
vm_object_t ksobj;
vm_offset_t ks;
struct kstack_cache_entry *ks_ce;
int pages;
pages = td->td_kstack_pages;
ksobj = td->td_kstack_obj;
ks = td->td_kstack;
td->td_kstack = 0;
td->td_kstack_pages = 0;
if (pages == kstack_pages && kstacks <= kstack_cache_size) {
ks_ce = (struct kstack_cache_entry *)ks;
ks_ce->ksobj = ksobj;
mtx_lock(&kstack_cache_mtx);
ks_ce->next_ks_entry = kstack_cache;
kstack_cache = ks_ce;
mtx_unlock(&kstack_cache_mtx);
return;
}
vm_thread_stack_dispose(ksobj, ks, pages);
}
static void
vm_thread_stack_lowmem(void *nulll)
{
struct kstack_cache_entry *ks_ce, *ks_ce1;
mtx_lock(&kstack_cache_mtx);
ks_ce = kstack_cache;
kstack_cache = NULL;
mtx_unlock(&kstack_cache_mtx);
while (ks_ce != NULL) {
ks_ce1 = ks_ce;
ks_ce = ks_ce->next_ks_entry;
vm_thread_stack_dispose(ks_ce1->ksobj, (vm_offset_t)ks_ce1,
kstack_pages);
}
}
static void
kstack_cache_init(void *nulll)
{
EVENTHANDLER_REGISTER(vm_lowmem, vm_thread_stack_lowmem, NULL,
EVENTHANDLER_PRI_ANY);
}
SYSINIT(vm_kstacks, SI_SUB_KTHREAD_INIT, SI_ORDER_ANY, kstack_cache_init, NULL);
#ifdef KSTACK_USAGE_PROF
/*
* Track maximum stack used by a thread in kernel.
*/
static int max_kstack_used;
SYSCTL_INT(_debug, OID_AUTO, max_kstack_used, CTLFLAG_RD,
&max_kstack_used, 0,
"Maxiumum stack depth used by a thread in kernel");
void
intr_prof_stack_use(struct thread *td, struct trapframe *frame)
{
vm_offset_t stack_top;
vm_offset_t current;
int used, prev_used;
/*
* Testing for interrupted kernel mode isn't strictly
* needed. It optimizes the execution, since interrupts from
* usermode will have only the trap frame on the stack.
*/
if (TRAPF_USERMODE(frame))
return;
stack_top = td->td_kstack + td->td_kstack_pages * PAGE_SIZE;
current = (vm_offset_t)(uintptr_t)&stack_top;
/*
* Try to detect if interrupt is using kernel thread stack.
* Hardware could use a dedicated stack for interrupt handling.
*/
if (stack_top <= current || current < td->td_kstack)
return;
used = stack_top - current;
for (;;) {
prev_used = max_kstack_used;
if (prev_used >= used)
break;
if (atomic_cmpset_int(&max_kstack_used, prev_used, used))
break;
}
}
#endif /* KSTACK_USAGE_PROF */
#ifndef NO_SWAPPING
/*
* Allow a thread's kernel stack to be paged out.
*/
static void
vm_thread_swapout(struct thread *td)
{
vm_object_t ksobj;
vm_page_t m;
int i, pages;
cpu_thread_swapout(td);
pages = td->td_kstack_pages;
ksobj = td->td_kstack_obj;
pmap_qremove(td->td_kstack, pages);
VM_OBJECT_WLOCK(ksobj);
for (i = 0; i < pages; i++) {
m = vm_page_lookup(ksobj, i);
if (m == NULL)
panic("vm_thread_swapout: kstack already missing?");
vm_page_dirty(m);
vm_page_lock(m);
vm_page_unwire(m, PQ_INACTIVE);
vm_page_unlock(m);
}
VM_OBJECT_WUNLOCK(ksobj);
}
/*
* Bring the kernel stack for a specified thread back in.
*/
static void
vm_thread_swapin(struct thread *td)
{
vm_object_t ksobj;
vm_page_t ma[KSTACK_MAX_PAGES];
int pages;
pages = td->td_kstack_pages;
ksobj = td->td_kstack_obj;
VM_OBJECT_WLOCK(ksobj);
for (int i = 0; i < pages; i++)
ma[i] = vm_page_grab(ksobj, i, VM_ALLOC_NORMAL |
VM_ALLOC_WIRED);
for (int i = 0; i < pages;) {
int j, a, count, rv;
vm_page_assert_xbusied(ma[i]);
if (ma[i]->valid == VM_PAGE_BITS_ALL) {
vm_page_xunbusy(ma[i]);
i++;
continue;
}
vm_object_pip_add(ksobj, 1);
for (j = i + 1; j < pages; j++)
if (ma[j]->valid == VM_PAGE_BITS_ALL)
break;
rv = vm_pager_has_page(ksobj, ma[i]->pindex, NULL, &a);
KASSERT(rv == 1, ("%s: missing page %p", __func__, ma[i]));
count = min(a + 1, j - i);
rv = vm_pager_get_pages(ksobj, ma + i, count, NULL, NULL);
KASSERT(rv == VM_PAGER_OK, ("%s: cannot get kstack for proc %d",
__func__, td->td_proc->p_pid));
vm_object_pip_wakeup(ksobj);
for (j = i; j < i + count; j++)
vm_page_xunbusy(ma[j]);
i += count;
}
VM_OBJECT_WUNLOCK(ksobj);
pmap_qenter(td->td_kstack, ma, pages);
cpu_thread_swapin(td);
}
#endif /* !NO_SWAPPING */
/*
* Implement fork's actions on an address space.
* Here we arrange for the address space to be copied or referenced,
* allocate a user struct (pcb and kernel stack), then call the
* machine-dependent layer to fill those in and make the new process
* ready to run. The new process is set up so that it returns directly
* to user mode to avoid stack copying and relocation problems.
*/
int
vm_forkproc(td, p2, td2, vm2, flags)
struct thread *td;
struct proc *p2;
struct thread *td2;
struct vmspace *vm2;
int flags;
{
struct proc *p1 = td->td_proc;
int error;
if ((flags & RFPROC) == 0) {
/*
* Divorce the memory, if it is shared, essentially
* this changes shared memory amongst threads, into
* COW locally.
*/
if ((flags & RFMEM) == 0) {
if (p1->p_vmspace->vm_refcnt > 1) {
error = vmspace_unshare(p1);
if (error)
return (error);
}
}
cpu_fork(td, p2, td2, flags);
return (0);
}
if (flags & RFMEM) {
p2->p_vmspace = p1->p_vmspace;
atomic_add_int(&p1->p_vmspace->vm_refcnt, 1);
}
while (vm_page_count_severe()) {
VM_WAIT;
}
if ((flags & RFMEM) == 0) {
p2->p_vmspace = vm2;
if (p1->p_vmspace->vm_shm)
shmfork(p1, p2);
}
/*
* cpu_fork will copy and update the pcb, set up the kernel stack,
* and make the child ready to run.
*/
cpu_fork(td, p2, td2, flags);
return (0);
}
/*
* Called after process has been wait(2)'ed upon and is being reaped.
* The idea is to reclaim resources that we could not reclaim while
* the process was still executing.
*/
void
vm_waitproc(p)
struct proc *p;
{
vmspace_exitfree(p); /* and clean-out the vmspace */
}
void
faultin(p)
struct proc *p;
{
#ifdef NO_SWAPPING
PROC_LOCK_ASSERT(p, MA_OWNED);
if ((p->p_flag & P_INMEM) == 0)
panic("faultin: proc swapped out with NO_SWAPPING!");
#else /* !NO_SWAPPING */
struct thread *td;
PROC_LOCK_ASSERT(p, MA_OWNED);
/*
* If another process is swapping in this process,
* just wait until it finishes.
*/
if (p->p_flag & P_SWAPPINGIN) {
while (p->p_flag & P_SWAPPINGIN)
msleep(&p->p_flag, &p->p_mtx, PVM, "faultin", 0);
return;
}
if ((p->p_flag & P_INMEM) == 0) {
/*
* Don't let another thread swap process p out while we are
* busy swapping it in.
*/
++p->p_lock;
p->p_flag |= P_SWAPPINGIN;
PROC_UNLOCK(p);
/*
* We hold no lock here because the list of threads
* can not change while all threads in the process are
* swapped out.
*/
FOREACH_THREAD_IN_PROC(p, td)
vm_thread_swapin(td);
PROC_LOCK(p);
swapclear(p);
p->p_swtick = ticks;
wakeup(&p->p_flag);
/* Allow other threads to swap p out now. */
--p->p_lock;
}
#endif /* NO_SWAPPING */
}
/*
* This swapin algorithm attempts to swap-in processes only if there
* is enough space for them. Of course, if a process waits for a long
* time, it will be swapped in anyway.
*/
void
swapper(void)
{
struct proc *p;
struct thread *td;
struct proc *pp;
int slptime;
int swtime;
int ppri;
int pri;
loop:
if (vm_page_count_min()) {
VM_WAIT;
goto loop;
}
pp = NULL;
ppri = INT_MIN;
sx_slock(&allproc_lock);
FOREACH_PROC_IN_SYSTEM(p) {
PROC_LOCK(p);
if (p->p_state == PRS_NEW ||
p->p_flag & (P_SWAPPINGOUT | P_SWAPPINGIN | P_INMEM)) {
PROC_UNLOCK(p);
continue;
}
swtime = (ticks - p->p_swtick) / hz;
FOREACH_THREAD_IN_PROC(p, td) {
/*
* An otherwise runnable thread of a process
* swapped out has only the TDI_SWAPPED bit set.
*
*/
thread_lock(td);
if (td->td_inhibitors == TDI_SWAPPED) {
slptime = (ticks - td->td_slptick) / hz;
pri = swtime + slptime;
if ((td->td_flags & TDF_SWAPINREQ) == 0)
pri -= p->p_nice * 8;
/*
* if this thread is higher priority
* and there is enough space, then select
* this process instead of the previous
* selection.
*/
if (pri > ppri) {
pp = p;
ppri = pri;
}
}
thread_unlock(td);
}
PROC_UNLOCK(p);
}
sx_sunlock(&allproc_lock);
/*
* Nothing to do, back to sleep.
*/
if ((p = pp) == NULL) {
tsleep(&proc0, PVM, "swapin", MAXSLP * hz / 2);
goto loop;
}
PROC_LOCK(p);
/*
* Another process may be bringing or may have already
* brought this process in while we traverse all threads.
* Or, this process may even be being swapped out again.
*/
if (p->p_flag & (P_INMEM | P_SWAPPINGOUT | P_SWAPPINGIN)) {
PROC_UNLOCK(p);
goto loop;
}
/*
* We would like to bring someone in. (only if there is space).
* [What checks the space? ]
*/
faultin(p);
PROC_UNLOCK(p);
goto loop;
}
void
kick_proc0(void)
{
wakeup(&proc0);
}
#ifndef NO_SWAPPING
/*
* Swap_idle_threshold1 is the guaranteed swapped in time for a process
*/
static int swap_idle_threshold1 = 2;
SYSCTL_INT(_vm, OID_AUTO, swap_idle_threshold1, CTLFLAG_RW,
&swap_idle_threshold1, 0, "Guaranteed swapped in time for a process");
/*
* Swap_idle_threshold2 is the time that a process can be idle before
* it will be swapped out, if idle swapping is enabled.
*/
static int swap_idle_threshold2 = 10;
SYSCTL_INT(_vm, OID_AUTO, swap_idle_threshold2, CTLFLAG_RW,
&swap_idle_threshold2, 0, "Time before a process will be swapped out");
/*
* First, if any processes have been sleeping or stopped for at least
* "swap_idle_threshold1" seconds, they are swapped out. If, however,
* no such processes exist, then the longest-sleeping or stopped
* process is swapped out. Finally, and only as a last resort, if
* there are no sleeping or stopped processes, the longest-resident
* process is swapped out.
*/
void
swapout_procs(action)
int action;
{
struct proc *p;
struct thread *td;
int didswap = 0;
retry:
sx_slock(&allproc_lock);
FOREACH_PROC_IN_SYSTEM(p) {
struct vmspace *vm;
int minslptime = 100000;
int slptime;
PROC_LOCK(p);
/*
* Watch out for a process in
* creation. It may have no
* address space or lock yet.
*/
if (p->p_state == PRS_NEW) {
PROC_UNLOCK(p);
continue;
}
/*
* An aio daemon switches its
* address space while running.
* Perform a quick check whether
* a process has P_SYSTEM.
* Filter out exiting processes.
*/
if ((p->p_flag & (P_SYSTEM | P_WEXIT)) != 0) {
PROC_UNLOCK(p);
continue;
}
_PHOLD_LITE(p);
PROC_UNLOCK(p);
sx_sunlock(&allproc_lock);
/*
* Do not swapout a process that
* is waiting for VM data
* structures as there is a possible
* deadlock. Test this first as
* this may block.
*
* Lock the map until swapout
* finishes, or a thread of this
* process may attempt to alter
* the map.
*/
vm = vmspace_acquire_ref(p);
if (vm == NULL)
goto nextproc2;
if (!vm_map_trylock(&vm->vm_map))
goto nextproc1;
PROC_LOCK(p);
if (p->p_lock != 1 || (p->p_flag & (P_STOPPED_SINGLE |
P_TRACED | P_SYSTEM)) != 0)
goto nextproc;
/*
* only aiod changes vmspace, however it will be
* skipped because of the if statement above checking
* for P_SYSTEM
*/
if ((p->p_flag & (P_INMEM|P_SWAPPINGOUT|P_SWAPPINGIN)) != P_INMEM)
goto nextproc;
switch (p->p_state) {
default:
/* Don't swap out processes in any sort
* of 'special' state. */
break;
case PRS_NORMAL:
/*
* do not swapout a realtime process
* Check all the thread groups..
*/
FOREACH_THREAD_IN_PROC(p, td) {
thread_lock(td);
if (PRI_IS_REALTIME(td->td_pri_class)) {
thread_unlock(td);
goto nextproc;
}
slptime = (ticks - td->td_slptick) / hz;
/*
* Guarantee swap_idle_threshold1
* time in memory.
*/
if (slptime < swap_idle_threshold1) {
thread_unlock(td);
goto nextproc;
}
/*
* Do not swapout a process if it is
* waiting on a critical event of some
* kind or there is a thread whose
* pageable memory may be accessed.
*
* This could be refined to support
* swapping out a thread.
*/
if (!thread_safetoswapout(td)) {
thread_unlock(td);
goto nextproc;
}
/*
* If the system is under memory stress,
* or if we are swapping
* idle processes >= swap_idle_threshold2,
* then swap the process out.
*/
if (((action & VM_SWAP_NORMAL) == 0) &&
(((action & VM_SWAP_IDLE) == 0) ||
(slptime < swap_idle_threshold2))) {
thread_unlock(td);
goto nextproc;
}
if (minslptime > slptime)
minslptime = slptime;
thread_unlock(td);
}
/*
* If the pageout daemon didn't free enough pages,
* or if this process is idle and the system is
* configured to swap proactively, swap it out.
*/
if ((action & VM_SWAP_NORMAL) ||
((action & VM_SWAP_IDLE) &&
(minslptime > swap_idle_threshold2))) {
_PRELE(p);
if (swapout(p) == 0)
didswap++;
PROC_UNLOCK(p);
vm_map_unlock(&vm->vm_map);
vmspace_free(vm);
goto retry;
}
}
nextproc:
PROC_UNLOCK(p);
vm_map_unlock(&vm->vm_map);
nextproc1:
vmspace_free(vm);
nextproc2:
sx_slock(&allproc_lock);
PRELE(p);
}
sx_sunlock(&allproc_lock);
/*
* If we swapped something out, and another process needed memory,
* then wakeup the sched process.
*/
if (didswap)
wakeup(&proc0);
}
static void
swapclear(p)
struct proc *p;
{
struct thread *td;
PROC_LOCK_ASSERT(p, MA_OWNED);
FOREACH_THREAD_IN_PROC(p, td) {
thread_lock(td);
td->td_flags |= TDF_INMEM;
td->td_flags &= ~TDF_SWAPINREQ;
TD_CLR_SWAPPED(td);
if (TD_CAN_RUN(td))
if (setrunnable(td)) {
#ifdef INVARIANTS
/*
* XXX: We just cleared TDI_SWAPPED
* above and set TDF_INMEM, so this
* should never happen.
*/
panic("not waking up swapper");
#endif
}
thread_unlock(td);
}
p->p_flag &= ~(P_SWAPPINGIN|P_SWAPPINGOUT);
p->p_flag |= P_INMEM;
}
static int
swapout(p)
struct proc *p;
{
struct thread *td;
PROC_LOCK_ASSERT(p, MA_OWNED);
#if defined(SWAP_DEBUG)
printf("swapping out %d\n", p->p_pid);
#endif
/*
* The states of this process and its threads may have changed
* by now. Assuming that there is only one pageout daemon thread,
* this process should still be in memory.
*/
KASSERT((p->p_flag & (P_INMEM|P_SWAPPINGOUT|P_SWAPPINGIN)) == P_INMEM,
("swapout: lost a swapout race?"));
/*
* remember the process resident count
*/
p->p_vmspace->vm_swrss = vmspace_resident_count(p->p_vmspace);
/*
* Check and mark all threads before we proceed.
*/
p->p_flag &= ~P_INMEM;
p->p_flag |= P_SWAPPINGOUT;
FOREACH_THREAD_IN_PROC(p, td) {
thread_lock(td);
if (!thread_safetoswapout(td)) {
thread_unlock(td);
swapclear(p);
return (EBUSY);
}
td->td_flags &= ~TDF_INMEM;
TD_SET_SWAPPED(td);
thread_unlock(td);
}
td = FIRST_THREAD_IN_PROC(p);
++td->td_ru.ru_nswap;
PROC_UNLOCK(p);
/*
* This list is stable because all threads are now prevented from
* running. The list is only modified in the context of a running
* thread in this process.
*/
FOREACH_THREAD_IN_PROC(p, td)
vm_thread_swapout(td);
PROC_LOCK(p);
p->p_flag &= ~P_SWAPPINGOUT;
p->p_swtick = ticks;
return (0);
}
#endif /* !NO_SWAPPING */