FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_zeroidle.c
1 /*-
2 * Copyright (c) 1994 John Dyson
3 * Copyright (c) 2001 Matt Dillon
4 *
5 * All Rights Reserved.
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 4. Neither the name of the University nor the names of its contributors
15 * may be used to endorse or promote products derived from this software
16 * without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
19 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
20 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
22 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
24 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
25 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
26 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
27 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
28 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 *
30 * from: @(#)vm_machdep.c 7.3 (Berkeley) 5/13/91
31 * Utah $Hdr: vm_machdep.c 1.16.1.1 89/06/23$
32 */
33
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD: releng/5.2/sys/vm/vm_zeroidle.c 118848 2003-08-12 23:24:05Z imp $");
36
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/kernel.h>
40 #include <sys/proc.h>
41 #include <sys/resourcevar.h>
42 #include <sys/vmmeter.h>
43 #include <sys/lock.h>
44 #include <sys/mutex.h>
45 #include <sys/sched.h>
46 #include <sys/sysctl.h>
47 #include <sys/kthread.h>
48
49 #include <vm/vm.h>
50 #include <vm/vm_page.h>
51
52 SYSCTL_DECL(_vm_stats_misc);
53
54 static int cnt_prezero;
55 SYSCTL_INT(_vm_stats_misc, OID_AUTO,
56 cnt_prezero, CTLFLAG_RD, &cnt_prezero, 0, "");
57
58 static int idlezero_enable = 1;
59 SYSCTL_INT(_vm, OID_AUTO, idlezero_enable, CTLFLAG_RW, &idlezero_enable, 0, "");
60 TUNABLE_INT("vm.idlezero_enable", &idlezero_enable);
61
62 static int idlezero_maxrun = 16;
63 SYSCTL_INT(_vm, OID_AUTO, idlezero_maxrun, CTLFLAG_RW, &idlezero_maxrun, 0, "");
64 TUNABLE_INT("vm.idlezero_maxrun", &idlezero_maxrun);
65
66 /*
67 * Implement the pre-zeroed page mechanism.
68 */
69
70 #define ZIDLE_LO(v) ((v) * 2 / 3)
71 #define ZIDLE_HI(v) ((v) * 4 / 5)
72
73 static int zero_state;
74
75 static int
76 vm_page_zero_check(void)
77 {
78
79 if (!idlezero_enable)
80 return 0;
81 /*
82 * Attempt to maintain approximately 1/2 of our free pages in a
83 * PG_ZERO'd state. Add some hysteresis to (attempt to) avoid
84 * generally zeroing a page when the system is near steady-state.
85 * Otherwise we might get 'flutter' during disk I/O / IPC or
86 * fast sleeps. We also do not want to be continuously zeroing
87 * pages because doing so may flush our L1 and L2 caches too much.
88 */
89 if (zero_state && vm_page_zero_count >= ZIDLE_LO(cnt.v_free_count))
90 return 0;
91 if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count))
92 return 0;
93 return 1;
94 }
95
96 static int
97 vm_page_zero_idle(void)
98 {
99 static int free_rover;
100 vm_page_t m;
101
102 mtx_lock_spin(&vm_page_queue_free_mtx);
103 zero_state = 0;
104 m = vm_pageq_find(PQ_FREE, free_rover, FALSE);
105 if (m != NULL && (m->flags & PG_ZERO) == 0) {
106 vm_pageq_remove_nowakeup(m);
107 mtx_unlock_spin(&vm_page_queue_free_mtx);
108 pmap_zero_page_idle(m);
109 mtx_lock_spin(&vm_page_queue_free_mtx);
110 m->flags |= PG_ZERO;
111 vm_pageq_enqueue(PQ_FREE + m->pc, m);
112 ++vm_page_zero_count;
113 ++cnt_prezero;
114 if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count))
115 zero_state = 1;
116 }
117 free_rover = (free_rover + PQ_PRIME2) & PQ_L2_MASK;
118 mtx_unlock_spin(&vm_page_queue_free_mtx);
119 return 1;
120 }
121
122
123 /* Called by vm_page_free to hint that a new page is available */
124 void
125 vm_page_zero_idle_wakeup(void)
126 {
127
128 if (idlezero_enable && vm_page_zero_check())
129 wakeup(&zero_state);
130 }
131
132 static void
133 vm_pagezero(void)
134 {
135 struct thread *td;
136 struct proc *p;
137 struct rtprio rtp;
138 int pages = 0;
139 int pri;
140
141 td = curthread;
142 p = td->td_proc;
143 rtp.prio = RTP_PRIO_MAX;
144 rtp.type = RTP_PRIO_IDLE;
145 mtx_lock_spin(&sched_lock);
146 rtp_to_pri(&rtp, td->td_ksegrp);
147 pri = td->td_priority;
148 mtx_unlock_spin(&sched_lock);
149 PROC_LOCK(p);
150 p->p_flag |= P_NOLOAD;
151 PROC_UNLOCK(p);
152
153 for (;;) {
154 if (vm_page_zero_check()) {
155 pages += vm_page_zero_idle();
156 if (pages > idlezero_maxrun || sched_runnable()) {
157 mtx_lock_spin(&sched_lock);
158 td->td_proc->p_stats->p_ru.ru_nvcsw++;
159 mi_switch();
160 mtx_unlock_spin(&sched_lock);
161 pages = 0;
162 }
163 } else {
164 tsleep(&zero_state, pri, "pgzero", hz * 300);
165 pages = 0;
166 }
167 }
168 }
169
170 static struct proc *pagezero_proc;
171 static struct kproc_desc pagezero_kp = {
172 "pagezero",
173 vm_pagezero,
174 &pagezero_proc
175 };
176 SYSINIT(pagezero, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, kproc_start, &pagezero_kp)
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