Messages in this thread | | | Subject | Re: [PATCH 0/3] OOM detection rework v4 | From | Tetsuo Handa <> | Date | Sat, 12 Mar 2016 01:49:26 +0900 |
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Michal Hocko wrote: > On Fri 11-03-16 22:32:02, Tetsuo Handa wrote: > > Michal Hocko wrote: > > > On Fri 11-03-16 19:45:29, Tetsuo Handa wrote: > > > > (Posting as a reply to this thread.) > > > > > > I really do not see how this is related to this thread. > > > > All allocating tasks are looping at > > > > /* > > * If we didn't make any progress and have a lot of > > * dirty + writeback pages then we should wait for > > * an IO to complete to slow down the reclaim and > > * prevent from pre mature OOM > > */ > > if (!did_some_progress && 2*(writeback + dirty) > reclaimable) { > > congestion_wait(BLK_RW_ASYNC, HZ/10); > > return true; > > } > > > > in should_reclaim_retry(). > > > > should_reclaim_retry() was added by OOM detection rework, wan't it? > > What happens without this patch applied. In other words, it all smells > like the IO got stuck somewhere and the direct reclaim cannot perform it > so we have to wait for the flushers to make a progress for us. Are those > stuck? Is the IO making any progress at all or it is just too slow and > it would finish actually. Wouldn't we just wait somewhere else in the > direct reclaim path instead.
As of next-20160311, CPU usage becomes 0% when this problem occurs.
If I remove
mm-use-watermak-checks-for-__gfp_repeat-high-order-allocations-checkpatch-fixes mm: use watermark checks for __GFP_REPEAT high order allocations mm: throttle on IO only when there are too many dirty and writeback pages mm-oom-rework-oom-detection-checkpatch-fixes mm, oom: rework oom detection
then CPU usage becomes 60% and most of allocating tasks are looping at
/* * Acquire the oom lock. If that fails, somebody else is * making progress for us. */ if (!mutex_trylock(&oom_lock)) { *did_some_progress = 1; schedule_timeout_uninterruptible(1); return NULL; }
in __alloc_pages_may_oom() (i.e. OOM-livelock due to the OOM reaper disabled).
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