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authorDavid Rientjes <rientjes@google.com>2010-08-09 17:18:51 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-08-09 20:44:56 -0700
commit5e9d834a0e0c0485dfa487281ab9650fc37a3bb5 (patch)
treeb93cf4fd46b50b18f3fc118f1739a71dbdd8f340 /mm/oom_kill.c
parent6cf86ac6f36b638459a9a6c2576d5e655d41d451 (diff)
oom: sacrifice child with highest badness score for parent
When a task is chosen for oom kill, the oom killer first attempts to sacrifice a child not sharing its parent's memory instead. Unfortunately, this often kills in a seemingly random fashion based on the ordering of the selected task's child list. Additionally, it is not guaranteed at all to free a large amount of memory that we need to prevent additional oom killing in the very near future. Instead, we now only attempt to sacrifice the worst child not sharing its parent's memory, if one exists. The worst child is indicated with the highest badness() score. This serves two advantages: we kill a memory-hogging task more often, and we allow the configurable /proc/pid/oom_adj value to be considered as a factor in which child to kill. Reviewers may observe that the previous implementation would iterate through the children and attempt to kill each until one was successful and then the parent if none were found while the new code simply kills the most memory-hogging task or the parent. Note that the only time oom_kill_task() fails, however, is when a child does not have an mm or has a /proc/pid/oom_adj of OOM_DISABLE. badness() returns 0 for both cases, so the final oom_kill_task() will always succeed. Signed-off-by: David Rientjes <rientjes@google.com> Acked-by: Rik van Riel <riel@redhat.com> Acked-by: Nick Piggin <npiggin@suse.de> Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/oom_kill.c')
-rw-r--r--mm/oom_kill.c40
1 files changed, 29 insertions, 11 deletions
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 6f6e04c40c9..7c8488f6a3f 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -362,10 +362,10 @@ static void dump_tasks(const struct mem_cgroup *mem)
static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
struct mem_cgroup *mem)
{
+ task_lock(current);
pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
"oom_adj=%d\n",
current->comm, gfp_mask, order, current->signal->oom_adj);
- task_lock(current);
cpuset_print_task_mems_allowed(current);
task_unlock(current);
dump_stack();
@@ -436,8 +436,11 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
unsigned long points, struct mem_cgroup *mem,
const char *message)
{
- struct task_struct *c;
+ struct task_struct *victim = p;
+ struct task_struct *child;
struct task_struct *t = p;
+ unsigned long victim_points = 0;
+ struct timespec uptime;
if (printk_ratelimit())
dump_header(p, gfp_mask, order, mem);
@@ -451,22 +454,37 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
return 0;
}
- printk(KERN_ERR "%s: kill process %d (%s) score %li or a child\n",
- message, task_pid_nr(p), p->comm, points);
+ task_lock(p);
+ pr_err("%s: Kill process %d (%s) score %lu or sacrifice child\n",
+ message, task_pid_nr(p), p->comm, points);
+ task_unlock(p);
- /* Try to kill a child first */
+ /*
+ * If any of p's children has a different mm and is eligible for kill,
+ * the one with the highest badness() score is sacrificed for its
+ * parent. This attempts to lose the minimal amount of work done while
+ * still freeing memory.
+ */
+ do_posix_clock_monotonic_gettime(&uptime);
do {
- list_for_each_entry(c, &t->children, sibling) {
- if (c->mm == p->mm)
+ list_for_each_entry(child, &t->children, sibling) {
+ unsigned long child_points;
+
+ if (child->mm == p->mm)
continue;
- if (mem && !task_in_mem_cgroup(c, mem))
+ if (mem && !task_in_mem_cgroup(child, mem))
continue;
- if (!oom_kill_task(c))
- return 0;
+
+ /* badness() returns 0 if the thread is unkillable */
+ child_points = badness(child, uptime.tv_sec);
+ if (child_points > victim_points) {
+ victim = child;
+ victim_points = child_points;
+ }
}
} while_each_thread(p, t);
- return oom_kill_task(p);
+ return oom_kill_task(victim);
}
#ifdef CONFIG_CGROUP_MEM_RES_CTLR