![David Rientjes](/assets/img/avatar_default.png)
The task handoff notifier leaks task_struct since it never gets freed after the callback returns NOTIFY_OK, which means it is responsible for doing so. It turns out the lowmemorykiller actually doesn't need this notifier at all. It's used to prevent unnecessary killing by waiting for a thread to exit as a result of lowmem_shrink(), however, it's possible to do this in the same way the kernel oom killer works by setting TIF_MEMDIE and avoid killing if we're still waiting for it to exit. The kernel oom killer will already automatically set TIF_MEMDIE for threads that are attempting to allocate memory that have a fatal signal. The thread selected by lowmem_shrink() will have such a signal after the lowmemorykiller sends it a SIGKILL, so this won't result in an unnecessary use of memory reserves for the thread to exit. This has the added benefit that we don't have to rely on CONFIG_PROFILING to prevent needlessly killing tasks. Reported-by: Werner Landgraf <w.landgraf@ru.ru> Cc: stable@vger.kernel.org Signed-off-by: David Rientjes <rientjes@google.com> Acked-by: Colin Cross <ccross@android.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
190 lines
5.5 KiB
C
190 lines
5.5 KiB
C
/* drivers/misc/lowmemorykiller.c
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*
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* The lowmemorykiller driver lets user-space specify a set of memory thresholds
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* where processes with a range of oom_score_adj values will get killed. Specify
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* the minimum oom_score_adj values in
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* /sys/module/lowmemorykiller/parameters/adj and the number of free pages in
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* /sys/module/lowmemorykiller/parameters/minfree. Both files take a comma
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* separated list of numbers in ascending order.
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*
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* For example, write "0,8" to /sys/module/lowmemorykiller/parameters/adj and
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* "1024,4096" to /sys/module/lowmemorykiller/parameters/minfree to kill
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* processes with a oom_score_adj value of 8 or higher when the free memory
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* drops below 4096 pages and kill processes with a oom_score_adj value of 0 or
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* higher when the free memory drops below 1024 pages.
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*
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* The driver considers memory used for caches to be free, but if a large
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* percentage of the cached memory is locked this can be very inaccurate
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* and processes may not get killed until the normal oom killer is triggered.
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*
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* Copyright (C) 2007-2008 Google, Inc.
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*
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* This software is licensed under the terms of the GNU General Public
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* License version 2, as published by the Free Software Foundation, and
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* may be copied, distributed, and modified under those terms.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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*/
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/oom.h>
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#include <linux/sched.h>
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#include <linux/rcupdate.h>
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#include <linux/profile.h>
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#include <linux/notifier.h>
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static uint32_t lowmem_debug_level = 2;
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static int lowmem_adj[6] = {
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0,
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1,
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6,
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12,
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};
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static int lowmem_adj_size = 4;
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static int lowmem_minfree[6] = {
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3 * 512, /* 6MB */
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2 * 1024, /* 8MB */
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4 * 1024, /* 16MB */
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16 * 1024, /* 64MB */
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};
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static int lowmem_minfree_size = 4;
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static unsigned long lowmem_deathpending_timeout;
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#define lowmem_print(level, x...) \
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do { \
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if (lowmem_debug_level >= (level)) \
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printk(x); \
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} while (0)
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static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
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{
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struct task_struct *tsk;
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struct task_struct *selected = NULL;
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int rem = 0;
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int tasksize;
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int i;
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int min_score_adj = OOM_SCORE_ADJ_MAX + 1;
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int selected_tasksize = 0;
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int selected_oom_score_adj;
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int array_size = ARRAY_SIZE(lowmem_adj);
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int other_free = global_page_state(NR_FREE_PAGES);
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int other_file = global_page_state(NR_FILE_PAGES) -
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global_page_state(NR_SHMEM);
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if (lowmem_adj_size < array_size)
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array_size = lowmem_adj_size;
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if (lowmem_minfree_size < array_size)
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array_size = lowmem_minfree_size;
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for (i = 0; i < array_size; i++) {
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if (other_free < lowmem_minfree[i] &&
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other_file < lowmem_minfree[i]) {
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min_score_adj = lowmem_adj[i];
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break;
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}
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}
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if (sc->nr_to_scan > 0)
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lowmem_print(3, "lowmem_shrink %lu, %x, ofree %d %d, ma %d\n",
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sc->nr_to_scan, sc->gfp_mask, other_free,
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other_file, min_score_adj);
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rem = global_page_state(NR_ACTIVE_ANON) +
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global_page_state(NR_ACTIVE_FILE) +
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global_page_state(NR_INACTIVE_ANON) +
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global_page_state(NR_INACTIVE_FILE);
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if (sc->nr_to_scan <= 0 || min_score_adj == OOM_SCORE_ADJ_MAX + 1) {
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lowmem_print(5, "lowmem_shrink %lu, %x, return %d\n",
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sc->nr_to_scan, sc->gfp_mask, rem);
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return rem;
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}
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selected_oom_score_adj = min_score_adj;
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rcu_read_lock();
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for_each_process(tsk) {
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struct task_struct *p;
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int oom_score_adj;
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if (tsk->flags & PF_KTHREAD)
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continue;
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p = find_lock_task_mm(tsk);
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if (!p)
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continue;
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if (test_tsk_thread_flag(p, TIF_MEMDIE) &&
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time_before_eq(jiffies, lowmem_deathpending_timeout)) {
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task_unlock(p);
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rcu_read_unlock();
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return 0;
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}
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oom_score_adj = p->signal->oom_score_adj;
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if (oom_score_adj < min_score_adj) {
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task_unlock(p);
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continue;
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}
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tasksize = get_mm_rss(p->mm);
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task_unlock(p);
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if (tasksize <= 0)
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continue;
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if (selected) {
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if (oom_score_adj < selected_oom_score_adj)
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continue;
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if (oom_score_adj == selected_oom_score_adj &&
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tasksize <= selected_tasksize)
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continue;
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}
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selected = p;
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selected_tasksize = tasksize;
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selected_oom_score_adj = oom_score_adj;
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lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",
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p->pid, p->comm, oom_score_adj, tasksize);
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}
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if (selected) {
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lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
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selected->pid, selected->comm,
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selected_oom_score_adj, selected_tasksize);
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lowmem_deathpending_timeout = jiffies + HZ;
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send_sig(SIGKILL, selected, 0);
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set_tsk_thread_flag(selected, TIF_MEMDIE);
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rem -= selected_tasksize;
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}
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lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n",
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sc->nr_to_scan, sc->gfp_mask, rem);
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rcu_read_unlock();
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return rem;
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}
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static struct shrinker lowmem_shrinker = {
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.shrink = lowmem_shrink,
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.seeks = DEFAULT_SEEKS * 16
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};
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static int __init lowmem_init(void)
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{
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register_shrinker(&lowmem_shrinker);
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return 0;
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}
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static void __exit lowmem_exit(void)
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{
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unregister_shrinker(&lowmem_shrinker);
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}
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module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
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module_param_array_named(adj, lowmem_adj, int, &lowmem_adj_size,
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S_IRUGO | S_IWUSR);
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module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
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S_IRUGO | S_IWUSR);
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module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
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module_init(lowmem_init);
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module_exit(lowmem_exit);
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MODULE_LICENSE("GPL");
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