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("$FreeBSD$"); 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#include <vm/vm_phys.h> 5579265Sdillon 56170816Salcstatic int idlezero_enable_default = 0; 57134461SiedowseTUNABLE_INT("vm.idlezero_enable", &idlezero_enable_default); 58134461Siedowse/* Defer setting the enable flag until the kthread is running. */ 59134461Siedowsestatic int idlezero_enable = 0; 60181239StrhodesSYSCTL_INT(_vm, OID_AUTO, idlezero_enable, CTLFLAG_RW, &idlezero_enable, 0, 61181239Strhodes "Allow the kernel to use idle cpu cycles to zero-out pages"); 6279265Sdillon/* 6379265Sdillon * Implement the pre-zeroed page mechanism. 6479265Sdillon */ 6579265Sdillon 6679265Sdillon#define ZIDLE_LO(v) ((v) * 2 / 3) 6779265Sdillon#define ZIDLE_HI(v) ((v) * 4 / 5) 6879265Sdillon 69137104Salcstatic boolean_t wakeup_needed = FALSE; 7082314Speterstatic int zero_state; 7182314Speter 7282314Speterstatic int 7382314Spetervm_page_zero_check(void) 7479265Sdillon{ 7579265Sdillon 7682314Speter if (!idlezero_enable) 77126588Sbde return (0); 7879265Sdillon /* 7979265Sdillon * Attempt to maintain approximately 1/2 of our free pages in a 8079265Sdillon * PG_ZERO'd state. Add some hysteresis to (attempt to) avoid 8179265Sdillon * generally zeroing a page when the system is near steady-state. 8279265Sdillon * Otherwise we might get 'flutter' during disk I/O / IPC or 8379265Sdillon * fast sleeps. We also do not want to be continuously zeroing 8479265Sdillon * pages because doing so may flush our L1 and L2 caches too much. 8579265Sdillon */ 86170170Sattilio if (zero_state && vm_page_zero_count >= ZIDLE_LO(cnt.v_free_count)) 87126588Sbde return (0); 88170170Sattilio if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count)) 89126588Sbde return (0); 90126588Sbde return (1); 9182314Speter} 9279265Sdillon 93161489Salcstatic void 9482314Spetervm_page_zero_idle(void) 9582314Speter{ 9682314Speter 97166637Salc mtx_assert(&vm_page_queue_free_mtx, MA_OWNED); 9882314Speter zero_state = 0; 99170816Salc if (vm_phys_zero_pages_idle()) { 100170170Sattilio if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count)) 10182314Speter zero_state = 1; 10282314Speter } 10382314Speter} 10482314Speter 105126588Sbde/* Called by vm_page_free to hint that a new page is available. */ 10682314Spetervoid 10782314Spetervm_page_zero_idle_wakeup(void) 10882314Speter{ 10982314Speter 110166637Salc mtx_assert(&vm_page_queue_free_mtx, MA_OWNED); 111137104Salc if (wakeup_needed && vm_page_zero_check()) { 112137104Salc wakeup_needed = FALSE; 11382314Speter wakeup(&zero_state); 114137104Salc } 11582314Speter} 11682314Speter 11782314Speterstatic void 118125314Sjeffvm_pagezero(void __unused *arg) 11982314Speter{ 12082314Speter 121134461Siedowse idlezero_enable = idlezero_enable_default; 12282314Speter 123166637Salc mtx_lock(&vm_page_queue_free_mtx); 12482314Speter for (;;) { 12582314Speter if (vm_page_zero_check()) { 126137268Sjhb vm_page_zero_idle(); 127131481Sjhb#ifndef PREEMPTION 128137268Sjhb if (sched_runnable()) { 129170307Sjeff thread_lock(curthread); 130178272Sjeff mi_switch(SW_VOL | SWT_IDLE, NULL); 131170307Sjeff thread_unlock(curthread); 13282314Speter } 133131481Sjhb#endif 13482314Speter } else { 135137104Salc wakeup_needed = TRUE; 136166637Salc msleep(&zero_state, &vm_page_queue_free_mtx, 0, 137166637Salc "pgzero", hz * 300); 13879265Sdillon } 13979265Sdillon } 14079265Sdillon} 14179265Sdillon 142125314Sjeffstatic void 143125314Sjeffpagezero_start(void __unused *arg) 144125314Sjeff{ 145125314Sjeff int error; 146198854Sattilio struct proc *p; 147141247Sssouhlal struct thread *td; 148125314Sjeff 149198854Sattilio error = kproc_create(vm_pagezero, NULL, &p, RFSTOPPED, 0, "pagezero"); 150125314Sjeff if (error) 151125314Sjeff panic("pagezero_start: error %d\n", error); 152198854Sattilio td = FIRST_THREAD_IN_PROC(p); 153170307Sjeff thread_lock(td); 154198854Sattilio 155198854Sattilio /* We're an idle task, don't count us in the load. */ 156198854Sattilio td->td_flags |= TDF_NOLOAD; 157163709Sjb sched_class(td, PRI_IDLE); 158141247Sssouhlal sched_prio(td, PRI_MAX_IDLE); 159166188Sjeff sched_add(td, SRQ_BORING); 160170307Sjeff thread_unlock(td); 161125314Sjeff} 162177253SrwatsonSYSINIT(pagezero, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, pagezero_start, NULL); 163