1 /*-
2 * Copyright (c) 2020 Emmanuel Vadot <[email protected]>
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
14 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
17 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
23 * SUCH DAMAGE.
24 */
25
26
27 #include <sys/cdefs.h>
28 #include <sys/param.h>
29 #include <sys/systm.h>
30 #include <sys/kernel.h>
31 #include <sys/queue.h>
32 #include <sys/eventhandler.h>
33 #include <sys/sx.h>
34
35 #include <linux/compat.h>
36 #include <linux/shrinker.h>
37
38 TAILQ_HEAD(, shrinker) lkpi_shrinkers = TAILQ_HEAD_INITIALIZER(lkpi_shrinkers);
39 static struct sx sx_shrinker;
40
41 int
linuxkpi_register_shrinker(struct shrinker * s)42 linuxkpi_register_shrinker(struct shrinker *s)
43 {
44
45 KASSERT(s != NULL, ("NULL shrinker"));
46 KASSERT(s->count_objects != NULL, ("NULL shrinker"));
47 KASSERT(s->scan_objects != NULL, ("NULL shrinker"));
48 sx_xlock(&sx_shrinker);
49 TAILQ_INSERT_TAIL(&lkpi_shrinkers, s, next);
50 sx_xunlock(&sx_shrinker);
51 return (0);
52 }
53
54 void
linuxkpi_unregister_shrinker(struct shrinker * s)55 linuxkpi_unregister_shrinker(struct shrinker *s)
56 {
57
58 sx_xlock(&sx_shrinker);
59 TAILQ_REMOVE(&lkpi_shrinkers, s, next);
60 sx_xunlock(&sx_shrinker);
61 }
62
63 void
linuxkpi_synchronize_shrinkers(void)64 linuxkpi_synchronize_shrinkers(void)
65 {
66
67 sx_xlock(&sx_shrinker);
68 sx_xunlock(&sx_shrinker);
69 }
70
71 #define SHRINKER_BATCH 512
72
73 static void
shrinker_shrink(struct shrinker * s)74 shrinker_shrink(struct shrinker *s)
75 {
76 struct shrink_control sc;
77 unsigned long can_free;
78 unsigned long batch;
79 unsigned long scanned = 0;
80 unsigned long ret;
81
82 can_free = s->count_objects(s, &sc);
83 if (can_free <= 0)
84 return;
85
86 batch = s->batch ? s->batch : SHRINKER_BATCH;
87 while (scanned <= can_free) {
88 sc.nr_to_scan = batch;
89 ret = s->scan_objects(s, &sc);
90 if (ret == SHRINK_STOP)
91 break;
92 scanned += batch;
93 }
94 }
95
96 static void
linuxkpi_vm_lowmem(void * arg __unused)97 linuxkpi_vm_lowmem(void *arg __unused)
98 {
99 struct shrinker *s;
100
101 sx_xlock(&sx_shrinker);
102 TAILQ_FOREACH(s, &lkpi_shrinkers, next) {
103 shrinker_shrink(s);
104 }
105 sx_xunlock(&sx_shrinker);
106 }
107
108 static eventhandler_tag lowmem_tag;
109
110 static void
linuxkpi_sysinit_shrinker(void * arg __unused)111 linuxkpi_sysinit_shrinker(void *arg __unused)
112 {
113
114 sx_init(&sx_shrinker, "lkpi-shrinker");
115 lowmem_tag = EVENTHANDLER_REGISTER(vm_lowmem, linuxkpi_vm_lowmem,
116 NULL, EVENTHANDLER_PRI_FIRST);
117 }
118
119 static void
linuxkpi_sysuninit_shrinker(void * arg __unused)120 linuxkpi_sysuninit_shrinker(void *arg __unused)
121 {
122
123 sx_destroy(&sx_shrinker);
124 EVENTHANDLER_DEREGISTER(vm_lowmem, lowmem_tag);
125 }
126
127 SYSINIT(linuxkpi_shrinker, SI_SUB_DRIVERS, SI_ORDER_ANY,
128 linuxkpi_sysinit_shrinker, NULL);
129 SYSUNINIT(linuxkpi_shrinker, SI_SUB_DRIVERS, SI_ORDER_ANY,
130 linuxkpi_sysuninit_shrinker, NULL);
131