vm_zeroidle.c revision 166188
179265Sdillon/*- 279265Sdillon * Copyright (c) 1994 John Dyson 379265Sdillon * Copyright (c) 2001 Matt Dillon 479265Sdillon * 5118848Simp * All Rights Reserved. 6118848Simp * Redistribution and use in source and binary forms, with or without 7118848Simp * modification, are permitted provided that the following conditions 8118848Simp * are met: 9118848Simp * 1. Redistributions of source code must retain the above copyright 10118848Simp * notice, this list of conditions and the following disclaimer. 11118848Simp * 2. Redistributions in binary form must reproduce the above copyright 12118848Simp * notice, this list of conditions and the following disclaimer in the 13118848Simp * documentation and/or other materials provided with the distribution. 14118848Simp * 4. Neither the name of the University nor the names of its contributors 15118848Simp * may be used to endorse or promote products derived from this software 16118848Simp * without specific prior written permission. 1779265Sdillon * 18118848Simp * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS 19118848Simp * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 20118848Simp * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21118848Simp * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY 22118848Simp * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23118848Simp * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE 24118848Simp * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 25118848Simp * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 26118848Simp * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 27118848Simp * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 28118848Simp * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29118848Simp * 3079265Sdillon * from: @(#)vm_machdep.c 7.3 (Berkeley) 5/13/91 3179265Sdillon * Utah $Hdr: vm_machdep.c 1.16.1.1 89/06/23$ 32126588Sbde * from: FreeBSD: .../i386/vm_machdep.c,v 1.165 2001/07/04 23:27:04 dillon 3379265Sdillon */ 3479265Sdillon 35116226Sobrien#include <sys/cdefs.h> 36116226Sobrien__FBSDID("$FreeBSD: head/sys/vm/vm_zeroidle.c 166188 2007-01-23 08:46:51Z jeff $"); 37116226Sobrien 38134649Sscottl#include <opt_sched.h> 39134649Sscottl 4079265Sdillon#include <sys/param.h> 4179265Sdillon#include <sys/systm.h> 4282314Speter#include <sys/kernel.h> 4379265Sdillon#include <sys/proc.h> 4479265Sdillon#include <sys/vmmeter.h> 4582314Speter#include <sys/lock.h> 4679265Sdillon#include <sys/mutex.h> 47104964Sjeff#include <sys/sched.h> 4879265Sdillon#include <sys/sysctl.h> 4982314Speter#include <sys/kthread.h> 50125314Sjeff#include <sys/unistd.h> 5179265Sdillon 5279265Sdillon#include <vm/vm.h> 5379265Sdillon#include <vm/vm_page.h> 5479265Sdillon 5579265Sdillonstatic int cnt_prezero; 56126588SbdeSYSCTL_INT(_vm_stats_misc, OID_AUTO, cnt_prezero, CTLFLAG_RD, 57126588Sbde &cnt_prezero, 0, ""); 5879265Sdillon 59134461Siedowsestatic int idlezero_enable_default = 1; 60134461SiedowseTUNABLE_INT("vm.idlezero_enable", &idlezero_enable_default); 61134461Siedowse/* Defer setting the enable flag until the kthread is running. */ 62134461Siedowsestatic int idlezero_enable = 0; 6382314SpeterSYSCTL_INT(_vm, OID_AUTO, idlezero_enable, CTLFLAG_RW, &idlezero_enable, 0, ""); 6482314Speter 6582314Speterstatic int idlezero_maxrun = 16; 6682314SpeterSYSCTL_INT(_vm, OID_AUTO, idlezero_maxrun, CTLFLAG_RW, &idlezero_maxrun, 0, ""); 6782314SpeterTUNABLE_INT("vm.idlezero_maxrun", &idlezero_maxrun); 6882314Speter 6979265Sdillon/* 7079265Sdillon * Implement the pre-zeroed page mechanism. 7179265Sdillon */ 7279265Sdillon 7379265Sdillon#define ZIDLE_LO(v) ((v) * 2 / 3) 7479265Sdillon#define ZIDLE_HI(v) ((v) * 4 / 5) 7579265Sdillon 76137104Salcstatic boolean_t wakeup_needed = FALSE; 7782314Speterstatic int zero_state; 7882314Speter 7982314Speterstatic int 8082314Spetervm_page_zero_check(void) 8179265Sdillon{ 8279265Sdillon 8382314Speter if (!idlezero_enable) 84126588Sbde return (0); 8579265Sdillon /* 8679265Sdillon * Attempt to maintain approximately 1/2 of our free pages in a 8779265Sdillon * PG_ZERO'd state. Add some hysteresis to (attempt to) avoid 8879265Sdillon * generally zeroing a page when the system is near steady-state. 8979265Sdillon * Otherwise we might get 'flutter' during disk I/O / IPC or 9079265Sdillon * fast sleeps. We also do not want to be continuously zeroing 9179265Sdillon * pages because doing so may flush our L1 and L2 caches too much. 9279265Sdillon */ 9379265Sdillon if (zero_state && vm_page_zero_count >= ZIDLE_LO(cnt.v_free_count)) 94126588Sbde return (0); 9579265Sdillon if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count)) 96126588Sbde return (0); 97126588Sbde return (1); 9882314Speter} 9979265Sdillon 100161489Salcstatic void 10182314Spetervm_page_zero_idle(void) 10282314Speter{ 10382314Speter static int free_rover; 10482314Speter vm_page_t m; 10582314Speter 10699625Speter mtx_lock_spin(&vm_page_queue_free_mtx); 10782314Speter zero_state = 0; 10882314Speter m = vm_pageq_find(PQ_FREE, free_rover, FALSE); 10982314Speter if (m != NULL && (m->flags & PG_ZERO) == 0) { 110100193Salc vm_pageq_remove_nowakeup(m); 11199625Speter mtx_unlock_spin(&vm_page_queue_free_mtx); 11299571Speter pmap_zero_page_idle(m); 11399625Speter mtx_lock_spin(&vm_page_queue_free_mtx); 114100331Salc m->flags |= PG_ZERO; 115100193Salc vm_pageq_enqueue(PQ_FREE + m->pc, m); 11682314Speter ++vm_page_zero_count; 11782314Speter ++cnt_prezero; 11882314Speter if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count)) 11982314Speter zero_state = 1; 12082314Speter } 121153940Snetchild free_rover = (free_rover + PQ_PRIME2) & PQ_COLORMASK; 12299625Speter mtx_unlock_spin(&vm_page_queue_free_mtx); 12382314Speter} 12482314Speter 125126588Sbde/* Called by vm_page_free to hint that a new page is available. */ 12682314Spetervoid 12782314Spetervm_page_zero_idle_wakeup(void) 12882314Speter{ 12982314Speter 130137104Salc mtx_assert(&vm_page_queue_mtx, MA_OWNED); 131137104Salc if (wakeup_needed && vm_page_zero_check()) { 132137104Salc wakeup_needed = FALSE; 13382314Speter wakeup(&zero_state); 134137104Salc } 13582314Speter} 13682314Speter 13782314Speterstatic void 138125314Sjeffvm_pagezero(void __unused *arg) 13982314Speter{ 14082314Speter 141134461Siedowse idlezero_enable = idlezero_enable_default; 14282314Speter 14382314Speter for (;;) { 14482314Speter if (vm_page_zero_check()) { 145137268Sjhb vm_page_zero_idle(); 146131481Sjhb#ifndef PREEMPTION 147137268Sjhb if (sched_runnable()) { 14882314Speter mtx_lock_spin(&sched_lock); 149131473Sjhb mi_switch(SW_VOL, NULL); 15082314Speter mtx_unlock_spin(&sched_lock); 15182314Speter } 152131481Sjhb#endif 15382314Speter } else { 154137104Salc vm_page_lock_queues(); 155137104Salc wakeup_needed = TRUE; 156137268Sjhb msleep(&zero_state, &vm_page_queue_mtx, 157157815Sjhb PDROP, "pgzero", hz * 300); 15879265Sdillon } 15979265Sdillon } 16079265Sdillon} 16179265Sdillon 162113070Sdesstatic struct proc *pagezero_proc; 163125314Sjeff 164125314Sjeffstatic void 165125314Sjeffpagezero_start(void __unused *arg) 166125314Sjeff{ 167125314Sjeff int error; 168141247Sssouhlal struct thread *td; 169125314Sjeff 170125314Sjeff error = kthread_create(vm_pagezero, NULL, &pagezero_proc, RFSTOPPED, 0, 171125314Sjeff "pagezero"); 172125314Sjeff if (error) 173125314Sjeff panic("pagezero_start: error %d\n", error); 174125314Sjeff /* 175125314Sjeff * We're an idle task, don't count us in the load. 176125314Sjeff */ 177125314Sjeff PROC_LOCK(pagezero_proc); 178125314Sjeff pagezero_proc->p_flag |= P_NOLOAD; 179125314Sjeff PROC_UNLOCK(pagezero_proc); 180125314Sjeff mtx_lock_spin(&sched_lock); 181141247Sssouhlal td = FIRST_THREAD_IN_PROC(pagezero_proc); 182163709Sjb sched_class(td, PRI_IDLE); 183141247Sssouhlal sched_prio(td, PRI_MAX_IDLE); 184166188Sjeff sched_add(td, SRQ_BORING); 185125314Sjeff mtx_unlock_spin(&sched_lock); 186125314Sjeff} 187125314SjeffSYSINIT(pagezero, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, pagezero_start, NULL) 188