/*- * Copyright (c) 1994 John Dyson * Copyright (c) 2001 Matt Dillon * * All rights reserved. Terms for use and redistribution * are covered by the BSD Copyright as found in /usr/src/COPYRIGHT. * * from: @(#)vm_machdep.c 7.3 (Berkeley) 5/13/91 * Utah $Hdr: vm_machdep.c 1.16.1.1 89/06/23$ * $FreeBSD$ */ #include #include #include #include #include #include #include #include #include #include #include #include SYSCTL_DECL(_vm_stats_misc); static int cnt_prezero; SYSCTL_INT(_vm_stats_misc, OID_AUTO, cnt_prezero, CTLFLAG_RD, &cnt_prezero, 0, ""); static int idlezero_enable = 0; SYSCTL_INT(_vm, OID_AUTO, idlezero_enable, CTLFLAG_RW, &idlezero_enable, 0, ""); TUNABLE_INT("vm.idlezero_enable", &idlezero_enable); static int idlezero_maxrun = 16; SYSCTL_INT(_vm, OID_AUTO, idlezero_maxrun, CTLFLAG_RW, &idlezero_maxrun, 0, ""); TUNABLE_INT("vm.idlezero_maxrun", &idlezero_maxrun); /* * Implement the pre-zeroed page mechanism. */ #define ZIDLE_LO(v) ((v) * 2 / 3) #define ZIDLE_HI(v) ((v) * 4 / 5) static int zero_state; static int vm_page_zero_check(void) { if (!idlezero_enable) return 0; /* * Attempt to maintain approximately 1/2 of our free pages in a * PG_ZERO'd state. Add some hysteresis to (attempt to) avoid * generally zeroing a page when the system is near steady-state. * Otherwise we might get 'flutter' during disk I/O / IPC or * fast sleeps. We also do not want to be continuously zeroing * pages because doing so may flush our L1 and L2 caches too much. */ if (zero_state && vm_page_zero_count >= ZIDLE_LO(cnt.v_free_count)) return 0; if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count)) return 0; return 1; } static int vm_page_zero_idle(void) { static int free_rover; vm_page_t m; mtx_lock(&Giant); zero_state = 0; m = vm_pageq_find(PQ_FREE, free_rover, FALSE); if (m != NULL && (m->flags & PG_ZERO) == 0) { vm_page_queues[m->queue].lcnt--; TAILQ_REMOVE(&vm_page_queues[m->queue].pl, m, pageq); m->queue = PQ_NONE; /* maybe drop out of Giant here */ pmap_zero_page(VM_PAGE_TO_PHYS(m)); /* and return here */ vm_page_flag_set(m, PG_ZERO); m->queue = PQ_FREE + m->pc; vm_page_queues[m->queue].lcnt++; TAILQ_INSERT_TAIL(&vm_page_queues[m->queue].pl, m, pageq); ++vm_page_zero_count; ++cnt_prezero; if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count)) zero_state = 1; } free_rover = (free_rover + PQ_PRIME2) & PQ_L2_MASK; mtx_unlock(&Giant); return 1; } /* Called by vm_page_free to hint that a new page is available */ void vm_page_zero_idle_wakeup(void) { if (vm_page_zero_check()) wakeup(&zero_state); } static void vm_pagezero(void) { struct proc *p = curproc; struct rtprio rtp; int pages = 0; rtp.prio = RTP_PRIO_MAX; rtp.type = RTP_PRIO_IDLE; mtx_lock_spin(&sched_lock); rtp_to_pri(&rtp, &p->p_pri); mtx_unlock_spin(&sched_lock); for (;;) { if (vm_page_zero_check()) { pages += vm_page_zero_idle(); if (pages > idlezero_maxrun) { mtx_lock_spin(&sched_lock); setrunqueue(p); p->p_stats->p_ru.ru_nvcsw++; mi_switch(); mtx_unlock_spin(&sched_lock); pages = 0; } } else { tsleep(&zero_state, PPAUSE, "pgzero", hz * 300); pages = 0; } } } static struct proc *pagezero; static struct kproc_desc pagezero_kp = { "pagezero", vm_pagezero, &pagezero }; SYSINIT(pagezero, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, kproc_start, &pagezero_kp)