On Wed 16-03-16 20:16:47, Tetsuo Handa wrote:
> Michal Hocko wrote:
[...]
> > And just to prevent from a confusion. I mean waking up also when
> > fatal_signal_pending and we do not really go down to selecting an oom
> > victim. Which would be worth a separate patch on top of course.
>
> I couldn't understand this part. The shortcut
>
> if (current->mm &&
> (fatal_signal_pending(current) || task_will_free_mem(current))) {
> mark_oom_victim(current);
> return true;
> }
>
> is not used for !__GFP_FS && !__GFP_NOFAIL allocation requests. I think
> we might go down to selecting an oom victim by out_of_memory() calls by
> not-yet-killed processes.
I meant something like the following. It would need some more tweaks
of course but here is the idea at least.
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 23b8b06152be..09e54bc0976c 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -686,6 +686,7 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p,
task_lock(p);
if (p->mm && task_will_free_mem(p)) {
mark_oom_victim(p);
+ wake_oom_reaper(p);
task_unlock(p);
put_task_struct(p);
return;
@@ -869,10 +870,22 @@ bool out_of_memory(struct oom_control *oc)
if (current->mm &&
(fatal_signal_pending(current) || task_will_free_mem(current))) {
mark_oom_victim(current);
+ wake_oom_reaper(current);
return true;
}
/*
+ * XXX: This is a weak reclaim context when FS metadata couldn't be
+ * reclaimed and so triggering the OOM killer could be really pre
+ * mature at this point. Traditionally have been looping in the page
+ * allocator and hoping for somebody else to make a forward progress
+ * for us. It would be better to simply fail those requests but we
+ * are not yet there so keep the tradition
+ */
+ if (!(gfp_mask & __GFP_FS))
+ return true;
+
+ /*
* Check if there were limitations on the allocation (only relevant for
* NUMA) that may require different handling.
*/
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d4d574dd0408..01121a89eb52 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2854,20 +2854,11 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
/* The OOM killer does not needlessly kill tasks for lowmem */
if (ac->high_zoneidx < ZONE_NORMAL)
goto out;
- /* The OOM killer does not compensate for IO-less reclaim */
- if (!(gfp_mask & __GFP_FS)) {
- /*
- * XXX: Page reclaim didn't yield anything,
- * and the OOM killer can't be invoked, but
- * keep looping as per tradition.
- *
- * But do not keep looping if oom_killer_disable()
- * was already called, for the system is trying to
- * enter a quiescent state during suspend.
- */
- *did_some_progress = !oom_killer_disabled;
- goto out;
- }
+ /*
+ * TODO once we are able to cope with GFP_NOFS allocation
+ * failures more gracefully just return and fail the allocation
+ * rather than trigger OOM
+ */
if (pm_suspended_storage())
goto out;
/* The OOM killer may not free memory on a specific node */
--
Michal Hocko
SUSE Labs
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