vm_zeroidle.c revision 170170
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 170170 2007-05-31 22:52:15Z attilio $"); 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> 54170816Salc 5579265Sdillonstatic int cnt_prezero; 56170816SalcSYSCTL_INT(_vm_stats_misc, OID_AUTO, cnt_prezero, CTLFLAG_RD, 57134461Siedowse &cnt_prezero, 0, ""); 58134461Siedowse 59134461Siedowsestatic int idlezero_enable_default = 1; 60181239StrhodesTUNABLE_INT("vm.idlezero_enable", &idlezero_enable_default); 61181239Strhodes/* Defer setting the enable flag until the kthread is running. */ 6279265Sdillonstatic int idlezero_enable = 0; 6379265SdillonSYSCTL_INT(_vm, OID_AUTO, idlezero_enable, CTLFLAG_RW, &idlezero_enable, 0, ""); 6479265Sdillon 6579265Sdillonstatic int idlezero_maxrun = 16; 6679265SdillonSYSCTL_INT(_vm, OID_AUTO, idlezero_maxrun, CTLFLAG_RW, &idlezero_maxrun, 0, ""); 6779265SdillonTUNABLE_INT("vm.idlezero_maxrun", &idlezero_maxrun); 6879265Sdillon 69137104Salc/* 7082314Speter * Implement the pre-zeroed page mechanism. 7182314Speter */ 7282314Speter 7382314Speter#define ZIDLE_LO(v) ((v) * 2 / 3) 7479265Sdillon#define ZIDLE_HI(v) ((v) * 4 / 5) 7579265Sdillon 7682314Speterstatic boolean_t wakeup_needed = FALSE; 77126588Sbdestatic int zero_state; 7879265Sdillon 7979265Sdillonstatic int 8079265Sdillonvm_page_zero_check(void) 8179265Sdillon{ 8279265Sdillon 8379265Sdillon if (!idlezero_enable) 8479265Sdillon return (0); 8579265Sdillon /* 86170170Sattilio * Attempt to maintain approximately 1/2 of our free pages in a 87126588Sbde * PG_ZERO'd state. Add some hysteresis to (attempt to) avoid 88170170Sattilio * generally zeroing a page when the system is near steady-state. 89126588Sbde * Otherwise we might get 'flutter' during disk I/O / IPC or 90126588Sbde * fast sleeps. We also do not want to be continuously zeroing 9182314Speter * pages because doing so may flush our L1 and L2 caches too much. 9279265Sdillon */ 93161489Salc if (zero_state && vm_page_zero_count >= ZIDLE_LO(cnt.v_free_count)) 9482314Speter return (0); 9582314Speter if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count)) 9682314Speter return (0); 97166637Salc return (1); 9882314Speter} 99170816Salc 100170170Sattiliostatic void 10182314Spetervm_page_zero_idle(void) 10282314Speter{ 10382314Speter static int free_rover; 10482314Speter vm_page_t m; 105126588Sbde 10682314Speter mtx_assert(&vm_page_queue_free_mtx, MA_OWNED); 10782314Speter zero_state = 0; 10882314Speter m = vm_pageq_find(PQ_FREE, free_rover, FALSE); 10982314Speter if (m != NULL && (m->flags & PG_ZERO) == 0) { 110166637Salc vm_pageq_remove_nowakeup(m); 111137104Salc mtx_unlock(&vm_page_queue_free_mtx); 112137104Salc pmap_zero_page_idle(m); 11382314Speter mtx_lock(&vm_page_queue_free_mtx); 114137104Salc m->flags |= PG_ZERO; 11582314Speter vm_pageq_enqueue(PQ_FREE + m->pc, m); 11682314Speter ++vm_page_zero_count; 11782314Speter ++cnt_prezero; 118125314Sjeff if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count)) 11982314Speter zero_state = 1; 12082314Speter } 121134461Siedowse free_rover = (free_rover + PQ_PRIME2) & PQ_COLORMASK; 12282314Speter} 123166637Salc 12482314Speter/* Called by vm_page_free to hint that a new page is available. */ 12582314Spetervoid 126137268Sjhbvm_page_zero_idle_wakeup(void) 127131481Sjhb{ 128137268Sjhb 129170307Sjeff mtx_assert(&vm_page_queue_free_mtx, MA_OWNED); 130178272Sjeff if (wakeup_needed && vm_page_zero_check()) { 131170307Sjeff wakeup_needed = FALSE; 13282314Speter wakeup(&zero_state); 133131481Sjhb } 13482314Speter} 135137104Salc 136166637Salcstatic void 137166637Salcvm_pagezero(void __unused *arg) 13879265Sdillon{ 13979265Sdillon 14079265Sdillon idlezero_enable = idlezero_enable_default; 14179265Sdillon 142125314Sjeff mtx_lock(&vm_page_queue_free_mtx); 143125314Sjeff for (;;) { 144125314Sjeff if (vm_page_zero_check()) { 145125314Sjeff vm_page_zero_idle(); 146198854Sattilio#ifndef PREEMPTION 147141247Sssouhlal if (sched_runnable()) { 148125314Sjeff mtx_lock_spin(&sched_lock); 149198854Sattilio mi_switch(SW_VOL, NULL); 150125314Sjeff mtx_unlock_spin(&sched_lock); 151125314Sjeff } 152198854Sattilio#endif 153170307Sjeff } else { 154198854Sattilio wakeup_needed = TRUE; 155198854Sattilio msleep(&zero_state, &vm_page_queue_free_mtx, 0, 156198854Sattilio "pgzero", hz * 300); 157163709Sjb } 158141247Sssouhlal } 159166188Sjeff} 160170307Sjeff 161125314Sjeffstatic struct proc *pagezero_proc; 162177253Srwatson 163static void 164pagezero_start(void __unused *arg) 165{ 166 int error; 167 struct thread *td; 168 169 error = kthread_create(vm_pagezero, NULL, &pagezero_proc, RFSTOPPED, 0, 170 "pagezero"); 171 if (error) 172 panic("pagezero_start: error %d\n", error); 173 /* 174 * We're an idle task, don't count us in the load. 175 */ 176 PROC_LOCK(pagezero_proc); 177 pagezero_proc->p_flag |= P_NOLOAD; 178 PROC_UNLOCK(pagezero_proc); 179 mtx_lock_spin(&sched_lock); 180 td = FIRST_THREAD_IN_PROC(pagezero_proc); 181 sched_class(td, PRI_IDLE); 182 sched_prio(td, PRI_MAX_IDLE); 183 sched_add(td, SRQ_BORING); 184 mtx_unlock_spin(&sched_lock); 185} 186SYSINIT(pagezero, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, pagezero_start, NULL) 187