1 /*- 2 * Copyright (c) 2020 Emmanuel Vadot <manu@FreeBSD.org> 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 * $FreeBSD$ 26 */ 27 28 29 #include <sys/cdefs.h> 30 __FBSDID("$FreeBSD$"); 31 32 #include <sys/param.h> 33 #include <sys/systm.h> 34 #include <sys/kernel.h> 35 #include <sys/queue.h> 36 #include <sys/eventhandler.h> 37 #include <sys/mutex.h> 38 39 #include <linux/shrinker.h> 40 41 TAILQ_HEAD(, shrinker) lkpi_shrinkers = TAILQ_HEAD_INITIALIZER(lkpi_shrinkers); 42 static struct mtx mtx_shrinker; 43 44 int 45 linuxkpi_register_shrinker(struct shrinker *s) 46 { 47 48 KASSERT(s != NULL, ("NULL shrinker")); 49 KASSERT(s->count_objects != NULL, ("NULL shrinker")); 50 KASSERT(s->scan_objects != NULL, ("NULL shrinker")); 51 mtx_lock(&mtx_shrinker); 52 TAILQ_INSERT_TAIL(&lkpi_shrinkers, s, next); 53 mtx_unlock(&mtx_shrinker); 54 return (0); 55 } 56 57 void 58 linuxkpi_unregister_shrinker(struct shrinker *s) 59 { 60 61 mtx_lock(&mtx_shrinker); 62 TAILQ_REMOVE(&lkpi_shrinkers, s, next); 63 mtx_unlock(&mtx_shrinker); 64 } 65 66 #define SHRINKER_BATCH 512 67 68 static void 69 shrinker_shrink(struct shrinker *s) 70 { 71 struct shrink_control sc; 72 unsigned long can_free; 73 unsigned long batch; 74 unsigned long scanned = 0; 75 unsigned long ret; 76 77 can_free = s->count_objects(s, &sc); 78 if (can_free <= 0) 79 return; 80 81 batch = s->batch ? s->batch : SHRINKER_BATCH; 82 while (scanned <= can_free) { 83 sc.nr_to_scan = batch; 84 ret = s->scan_objects(s, &sc); 85 if (ret == SHRINK_STOP) 86 break; 87 scanned += batch; 88 } 89 } 90 91 static void 92 linuxkpi_vm_lowmem(void *arg __unused) 93 { 94 struct shrinker *s; 95 96 mtx_lock(&mtx_shrinker); 97 TAILQ_FOREACH(s, &lkpi_shrinkers, next) { 98 shrinker_shrink(s); 99 } 100 mtx_unlock(&mtx_shrinker); 101 } 102 103 static eventhandler_tag lowmem_tag; 104 105 static void 106 linuxkpi_sysinit_shrinker(void *arg __unused) 107 { 108 109 mtx_init(&mtx_shrinker, "lkpi-shrinker", NULL, MTX_DEF); 110 lowmem_tag = EVENTHANDLER_REGISTER(vm_lowmem, linuxkpi_vm_lowmem, 111 NULL, EVENTHANDLER_PRI_FIRST); 112 } 113 114 static void 115 linuxkpi_sysuninit_shrinker(void *arg __unused) 116 { 117 118 mtx_destroy(&mtx_shrinker); 119 EVENTHANDLER_DEREGISTER(vm_lowmem, lowmem_tag); 120 } 121 122 SYSINIT(linuxkpi_shrinker, SI_SUB_DRIVERS, SI_ORDER_ANY, 123 linuxkpi_sysinit_shrinker, NULL); 124 SYSUNINIT(linuxkpi_shrinker, SI_SUB_DRIVERS, SI_ORDER_ANY, 125 linuxkpi_sysuninit_shrinker, NULL); 126