Below is a 2.6.17-rc4-mm3 patch that fixes a problem where the OOM killer was
unnecessarily killing system daemons in addition to memory-hogging user
processes. The patch fixes things so that the following assertion is
satisfied:
If a failed attempt to allocate memory triggers the OOM killer, then the
failed attempt must have occurred _after_ any process previously shot by
the OOM killer has cleaned out its mm_struct.
Thus we avoid situations where concurrent invocations of the OOM killer cause
more processes to be shot than necessary to resolve the OOM condition.
Signed-Off-By: David S. Peterson <[email protected]>
---
Changes in this version of patch:
- Loop over all tasks to determine whether OOM kill is in progress.
Eliminate OOM notify flag in mm_struct, etc.
diff -urNp -X dontdiff linux-2.6.17-rc5-mm1/mm/oom_kill.c linux-2.6.17-rc5-mm1-oom/mm/oom_kill.c
--- linux-2.6.17-rc5-mm1/mm/oom_kill.c 2006-05-30 14:05:53.000000000 -0700
+++ linux-2.6.17-rc5-mm1-oom/mm/oom_kill.c 2006-05-30 14:07:00.000000000 -0700
@@ -25,6 +25,23 @@
int sysctl_panic_on_oom;
/* #define DEBUG */
+/* Return 1 if OOM kill in progress. Else return 0. */
+int oom_kill_active(void)
+{
+ task_t *p, *q;
+
+ read_lock(&tasklist_lock);
+ do_each_thread(p, q) {
+ if (test_tsk_thread_flag(q, TIF_MEMDIE)) {
+ read_unlock(&tasklist_lock);
+ return 1;
+ }
+ } while_each_thread(p, q);
+ read_unlock(&tasklist_lock);
+
+ return 0;
+}
+
/**
* badness - calculate a numeric value for how bad this task has been
* @p: task struct of which task we should calculate
@@ -318,6 +335,7 @@ void out_of_memory(struct zonelist *zone
{
task_t *p;
unsigned long points = 0;
+ const char *msg = NULL;
if (printk_ratelimit()) {
printk("oom-killer: gfp_mask=0x%x, order=%d\n",
@@ -335,19 +353,19 @@ void out_of_memory(struct zonelist *zone
*/
switch (constrained_alloc(zonelist, gfp_mask)) {
case CONSTRAINT_MEMORY_POLICY:
- oom_kill_process(current, points,
- "No available memory (MPOL_BIND)");
+ p = current;
+ msg = "No available memory (MPOL_BIND)";
break;
case CONSTRAINT_CPUSET:
- oom_kill_process(current, points,
- "No available memory in cpuset");
+ p = current;
+ msg = "No available memory in cpuset";
break;
case CONSTRAINT_NONE:
if (sysctl_panic_on_oom)
panic("out of memory. panic_on_oom is selected\n");
-retry:
+
/*
* Rambo mode: Shoot down a process and hope it solves whatever
* issues we may have.
@@ -364,20 +382,16 @@ retry:
panic("Out of memory and no killable processes...\n");
}
- if (oom_kill_process(p, points, "Out of memory"))
- goto retry;
-
+ msg = "Out of memory";
break;
+
+ default:
+ BUG();
}
+ oom_kill_process(p, points, msg);
+
out:
read_unlock(&tasklist_lock);
cpuset_unlock();
-
- /*
- * Give "p" a good chance of killing itself before we
- * retry to allocate memory unless "p" is current
- */
- if (!test_thread_flag(TIF_MEMDIE))
- schedule_timeout_uninterruptible(1);
}
diff -urNp -X dontdiff linux-2.6.17-rc5-mm1/mm/page_alloc.c linux-2.6.17-rc5-mm1-oom/mm/page_alloc.c
--- linux-2.6.17-rc5-mm1/mm/page_alloc.c 2006-05-30 14:05:53.000000000 -0700
+++ linux-2.6.17-rc5-mm1-oom/mm/page_alloc.c 2006-05-30 14:07:00.000000000 -0700
@@ -992,6 +992,56 @@ static inline void set_page_owner(struct
}
#endif /* CONFIG_PAGE_OWNER */
+int oom_kill_active(void);
+
+/* If an OOM kill is not already in progress, try once more to allocate
+ * memory. If allocation fails this time, invoke the OOM killer.
+ */
+static struct page * oom_alloc(gfp_t gfp_mask, unsigned int order,
+ struct zonelist *zonelist)
+{
+ static DECLARE_MUTEX(sem);
+ struct page *page;
+
+ down(&sem);
+
+ /* Prevent parallel OOM kill operations. This fixes a problem where
+ * the OOM killer was observed shooting system daemons in addition to
+ * memory-hogging user processes.
+ */
+ if (oom_kill_active()) {
+ up(&sem);
+ goto out_sleep;
+ }
+
+ /* If we get here, we _know_ that any previous OOM killer victim has
+ * cleaned out its mm_struct. Therefore we should pick a victim to
+ * shoot if this allocation fails.
+ */
+ page = get_page_from_freelist(gfp_mask | __GFP_HARDWALL, order,
+ zonelist, ALLOC_WMARK_HIGH | ALLOC_CPUSET);
+
+ if (page) {
+ up(&sem);
+ return page;
+ }
+
+ /* Try to shoot a process. */
+ out_of_memory(zonelist, gfp_mask, order);
+ up(&sem);
+
+out_sleep:
+ /* Did we get shot by the OOM killer? If not, sleep for a while to
+ * avoid burning lots of CPU cycles looping in the memory allocator.
+ * If the OOM killer shot a process, this gives the victim a good
+ * chance to die before we retry allocation.
+ */
+ if (!test_thread_flag(TIF_MEMDIE))
+ schedule_timeout_uninterruptible(1);
+
+ return NULL;
+}
+
/*
* This is the 'heart' of the zoned buddy allocator.
*/
@@ -1102,18 +1152,9 @@ rebalance:
if (page)
goto got_pg;
} else if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)) {
- /*
- * Go through the zonelist yet one more time, keep
- * very high watermark here, this is only to catch
- * a parallel oom killing, we must fail if we're still
- * under heavy pressure.
- */
- page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, order,
- zonelist, ALLOC_WMARK_HIGH|ALLOC_CPUSET);
+ page = oom_alloc(gfp_mask, order, zonelist);
if (page)
goto got_pg;
-
- out_of_memory(zonelist, gfp_mask, order);
goto restart;
}
-
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