a8415c5a0d
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
172 lines
4.9 KiB
C
172 lines
4.9 KiB
C
/*-
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* Copyright (c) 1994 John Dyson
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* Copyright (c) 2001 Matt Dillon
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*
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* 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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* from: @(#)vm_machdep.c 7.3 (Berkeley) 5/13/91
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* Utah $Hdr: vm_machdep.c 1.16.1.1 89/06/23$
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* from: FreeBSD: .../i386/vm_machdep.c,v 1.165 2001/07/04 23:27:04 dillon
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <opt_sched.h>
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/proc.h>
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#include <sys/vmmeter.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/sched.h>
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#include <sys/sysctl.h>
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#include <sys/kthread.h>
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#include <sys/unistd.h>
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#include <vm/vm.h>
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#include <vm/vm_page.h>
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#include <vm/vm_phys.h>
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static int idlezero_enable_default = 0;
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TUNABLE_INT("vm.idlezero_enable", &idlezero_enable_default);
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/* Defer setting the enable flag until the kthread is running. */
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static int idlezero_enable = 0;
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SYSCTL_INT(_vm, OID_AUTO, idlezero_enable, CTLFLAG_RW, &idlezero_enable, 0, "");
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static int idlezero_maxrun = 16;
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SYSCTL_INT(_vm, OID_AUTO, idlezero_maxrun, CTLFLAG_RW, &idlezero_maxrun, 0, "");
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TUNABLE_INT("vm.idlezero_maxrun", &idlezero_maxrun);
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/*
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* Implement the pre-zeroed page mechanism.
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*/
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#define ZIDLE_LO(v) ((v) * 2 / 3)
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#define ZIDLE_HI(v) ((v) * 4 / 5)
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static boolean_t wakeup_needed = FALSE;
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static int zero_state;
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static int
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vm_page_zero_check(void)
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{
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if (!idlezero_enable)
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return (0);
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/*
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* Attempt to maintain approximately 1/2 of our free pages in a
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* PG_ZERO'd state. Add some hysteresis to (attempt to) avoid
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* generally zeroing a page when the system is near steady-state.
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* Otherwise we might get 'flutter' during disk I/O / IPC or
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* fast sleeps. We also do not want to be continuously zeroing
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* pages because doing so may flush our L1 and L2 caches too much.
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*/
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if (zero_state && vm_page_zero_count >= ZIDLE_LO(cnt.v_free_count))
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return (0);
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if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count))
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return (0);
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return (1);
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}
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static void
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vm_page_zero_idle(void)
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{
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mtx_assert(&vm_page_queue_free_mtx, MA_OWNED);
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zero_state = 0;
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if (vm_phys_zero_pages_idle()) {
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if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count))
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zero_state = 1;
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}
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}
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/* Called by vm_page_free to hint that a new page is available. */
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void
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vm_page_zero_idle_wakeup(void)
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{
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mtx_assert(&vm_page_queue_free_mtx, MA_OWNED);
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if (wakeup_needed && vm_page_zero_check()) {
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wakeup_needed = FALSE;
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wakeup(&zero_state);
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}
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}
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static void
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vm_pagezero(void __unused *arg)
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{
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idlezero_enable = idlezero_enable_default;
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mtx_lock(&vm_page_queue_free_mtx);
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for (;;) {
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if (vm_page_zero_check()) {
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vm_page_zero_idle();
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#ifndef PREEMPTION
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if (sched_runnable()) {
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thread_lock(curthread);
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mi_switch(SW_VOL, NULL);
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thread_unlock(curthread);
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}
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#endif
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} else {
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wakeup_needed = TRUE;
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msleep(&zero_state, &vm_page_queue_free_mtx, 0,
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"pgzero", hz * 300);
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}
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}
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}
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static struct proc *pagezero_proc;
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static void
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pagezero_start(void __unused *arg)
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{
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int error;
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struct thread *td;
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error = kthread_create(vm_pagezero, NULL, &pagezero_proc, RFSTOPPED, 0,
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"pagezero");
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if (error)
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panic("pagezero_start: error %d\n", error);
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/*
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* We're an idle task, don't count us in the load.
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*/
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PROC_LOCK(pagezero_proc);
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pagezero_proc->p_flag |= P_NOLOAD;
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PROC_UNLOCK(pagezero_proc);
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td = FIRST_THREAD_IN_PROC(pagezero_proc);
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thread_lock(td);
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sched_class(td, PRI_IDLE);
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sched_prio(td, PRI_MAX_IDLE);
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sched_add(td, SRQ_BORING);
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thread_unlock(td);
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}
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SYSINIT(pagezero, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, pagezero_start, NULL)
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