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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)
116 lines
3.1 KiB
C
116 lines
3.1 KiB
C
/*-
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* Copyright (c) 1998 Matthew Dillon. All Rights Reserved.
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
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* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
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* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/linker_set.h>
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#include <sys/lock.h>
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#include <sys/malloc.h>
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#include <sys/mutex.h>
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#include <sys/sysctl.h>
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#include <sys/proc.h>
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#include <sys/vmmeter.h>
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#include <sys/vnode.h>
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#include <vm/vm.h>
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#include <vm/vm_param.h>
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#include <vm/vm_kern.h>
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#include <vm/vm_object.h>
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#include <vm/vm_page.h>
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#include <vm/vm_pageout.h>
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#include <vm/vm_pager.h>
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#include <vm/vm_phys.h>
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#include <vm/vm_extern.h>
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struct vpgqueues vm_page_queues[PQ_MAXCOUNT];
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void
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vm_pageq_init(void)
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{
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int i;
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vm_page_queues[PQ_INACTIVE].cnt = &cnt.v_inactive_count;
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vm_page_queues[PQ_ACTIVE].cnt = &cnt.v_active_count;
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vm_page_queues[PQ_HOLD].cnt = &cnt.v_active_count;
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for (i = 0; i < PQ_COUNT; i++) {
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TAILQ_INIT(&vm_page_queues[i].pl);
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}
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}
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void
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vm_pageq_requeue(vm_page_t m)
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{
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int queue = VM_PAGE_GETQUEUE(m);
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struct vpgqueues *vpq;
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if (queue != PQ_NONE) {
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vpq = &vm_page_queues[queue];
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TAILQ_REMOVE(&vpq->pl, m, pageq);
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TAILQ_INSERT_TAIL(&vpq->pl, m, pageq);
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}
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}
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/*
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* vm_pageq_enqueue:
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*/
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void
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vm_pageq_enqueue(int queue, vm_page_t m)
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{
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struct vpgqueues *vpq;
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vpq = &vm_page_queues[queue];
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VM_PAGE_SETQUEUE2(m, queue);
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TAILQ_INSERT_TAIL(&vpq->pl, m, pageq);
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++*vpq->cnt;
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}
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/*
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* vm_pageq_remove:
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*
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* Remove a page from its queue.
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*
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* The queue containing the given page must be locked.
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* This routine may not block.
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*/
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void
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vm_pageq_remove(vm_page_t m)
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{
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int queue = VM_PAGE_GETQUEUE(m);
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struct vpgqueues *pq;
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if (queue != PQ_NONE) {
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VM_PAGE_SETQUEUE2(m, PQ_NONE);
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pq = &vm_page_queues[queue];
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TAILQ_REMOVE(&pq->pl, m, pageq);
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(*pq->cnt)--;
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}
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}
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