freebsd-nq/sys/vm/vm_object.h
Alan Cox 7bfda801a8 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

218 lines
7.7 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_object.h 8.3 (Berkeley) 1/12/94
*
*
* Copyright (c) 1987, 1990 Carnegie-Mellon University.
* All rights reserved.
*
* Authors: Avadis Tevanian, Jr., Michael Wayne Young
*
* 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.
*
* $FreeBSD$
*/
/*
* Virtual memory object module definitions.
*/
#ifndef _VM_OBJECT_
#define _VM_OBJECT_
#include <sys/queue.h>
#include <sys/_lock.h>
#include <sys/_mutex.h>
/*
* Types defined:
*
* vm_object_t Virtual memory object.
*
* List of locks
* (c) const until freed
*
*/
struct vm_object {
struct mtx mtx;
TAILQ_ENTRY(vm_object) object_list; /* list of all objects */
LIST_HEAD(, vm_object) shadow_head; /* objects that this is a shadow for */
LIST_ENTRY(vm_object) shadow_list; /* chain of shadow objects */
TAILQ_HEAD(, vm_page) memq; /* list of resident pages */
vm_page_t root; /* root of the resident page splay tree */
vm_pindex_t size; /* Object size */
int generation; /* generation ID */
int ref_count; /* How many refs?? */
int shadow_count; /* how many objects that this is a shadow for */
objtype_t type; /* type of pager */
u_short flags; /* see below */
u_short pg_color; /* (c) color of first page in obj */
u_short paging_in_progress; /* Paging (in or out) so don't collapse or destroy */
int resident_page_count; /* number of resident pages */
struct vm_object *backing_object; /* object that I'm a shadow of */
vm_ooffset_t backing_object_offset;/* Offset in backing object */
TAILQ_ENTRY(vm_object) pager_object_list; /* list of all objects of this pager type */
vm_page_t cache; /* root of the cache page splay tree */
void *handle;
union {
/*
* VNode pager
*
* vnp_size - current size of file
*/
struct {
off_t vnp_size;
} vnp;
/*
* Device pager
*
* devp_pglist - list of allocated pages
*/
struct {
TAILQ_HEAD(, vm_page) devp_pglist;
} devp;
/*
* Swap pager
*
* swp_bcount - number of swap 'swblock' metablocks, each
* contains up to 16 swapblk assignments.
* see vm/swap_pager.h
*/
struct {
int swp_bcount;
} swp;
} un_pager;
};
/*
* Flags
*/
#define OBJ_ACTIVE 0x0004 /* active objects */
#define OBJ_DEAD 0x0008 /* dead objects (during rundown) */
#define OBJ_NOSPLIT 0x0010 /* dont split this object */
#define OBJ_PIPWNT 0x0040 /* paging in progress wanted */
#define OBJ_MIGHTBEDIRTY 0x0100 /* object might be dirty */
#define OBJ_CLEANING 0x0200
#define OBJ_ONEMAPPING 0x2000 /* One USE (a single, non-forked) mapping flag */
#define OBJ_DISCONNECTWNT 0x4000 /* disconnect from vnode wanted */
#define OBJ_NEEDGIANT 0x8000 /* object requires Giant */
#define IDX_TO_OFF(idx) (((vm_ooffset_t)(idx)) << PAGE_SHIFT)
#define OFF_TO_IDX(off) ((vm_pindex_t)(((vm_ooffset_t)(off)) >> PAGE_SHIFT))
#ifdef _KERNEL
#define OBJPC_SYNC 0x1 /* sync I/O */
#define OBJPC_INVAL 0x2 /* invalidate */
#define OBJPC_NOSYNC 0x4 /* skip if PG_NOSYNC */
TAILQ_HEAD(object_q, vm_object);
extern struct object_q vm_object_list; /* list of allocated objects */
extern struct mtx vm_object_list_mtx; /* lock for object list and count */
extern struct vm_object kernel_object_store;
extern struct vm_object kmem_object_store;
#define kernel_object (&kernel_object_store)
#define kmem_object (&kmem_object_store)
#define VM_OBJECT_LOCK(object) mtx_lock(&(object)->mtx)
#define VM_OBJECT_LOCK_ASSERT(object, type) \
mtx_assert(&(object)->mtx, (type))
#define VM_OBJECT_LOCK_INIT(object, type) \
mtx_init(&(object)->mtx, "vm object", \
(type), MTX_DEF | MTX_DUPOK)
#define VM_OBJECT_LOCKED(object) mtx_owned(&(object)->mtx)
#define VM_OBJECT_MTX(object) (&(object)->mtx)
#define VM_OBJECT_TRYLOCK(object) mtx_trylock(&(object)->mtx)
#define VM_OBJECT_UNLOCK(object) mtx_unlock(&(object)->mtx)
/*
* The object must be locked or thread private.
*/
static __inline void
vm_object_set_flag(vm_object_t object, u_short bits)
{
object->flags |= bits;
}
void vm_object_clear_flag(vm_object_t object, u_short bits);
void vm_object_pip_add(vm_object_t object, short i);
void vm_object_pip_subtract(vm_object_t object, short i);
void vm_object_pip_wakeup(vm_object_t object);
void vm_object_pip_wakeupn(vm_object_t object, short i);
void vm_object_pip_wait(vm_object_t object, char *waitid);
vm_object_t vm_object_allocate (objtype_t, vm_pindex_t);
void _vm_object_allocate (objtype_t, vm_pindex_t, vm_object_t);
boolean_t vm_object_coalesce(vm_object_t, vm_ooffset_t, vm_size_t, vm_size_t);
void vm_object_collapse (vm_object_t);
void vm_object_deallocate (vm_object_t);
void vm_object_terminate (vm_object_t);
void vm_object_set_writeable_dirty (vm_object_t);
void vm_object_init (void);
void vm_object_page_clean (vm_object_t, vm_pindex_t, vm_pindex_t, boolean_t);
void vm_object_page_remove (vm_object_t, vm_pindex_t, vm_pindex_t, boolean_t);
void vm_object_reference (vm_object_t);
void vm_object_reference_locked(vm_object_t);
void vm_object_shadow (vm_object_t *, vm_ooffset_t *, vm_size_t);
void vm_object_split(vm_map_entry_t);
void vm_object_sync(vm_object_t, vm_ooffset_t, vm_size_t, boolean_t,
boolean_t);
void vm_object_madvise (vm_object_t, vm_pindex_t, int, int);
#endif /* _KERNEL */
#endif /* _VM_OBJECT_ */