Messages in this thread | | | Date | Fri, 26 Mar 2021 11:22:54 +0000 | From | Aaron Tomlin <> | Subject | Re: [PATCH] mm/page_alloc: try oom if reclaim is unable to make forward progress |
| |
Hi Michal,
On Fri 2021-03-26 09:16 +0100, Michal Hocko wrote: > The oom killer is never triggered for costly allocation request.
Yes - I agree. Looking at __alloc_pages_may_oom() I can see for a costly order allocation request the OOM killer is explicitly not used. If I understand correctly, the patch I proposed was for the following scenarios:
1. The costly order allocation request to fail when "some" progress is made (i.e. order-0) and the last compaction request was "skipped"
2. A non-costly order allocation request that is unable to make any progress and failed over the maximum reclaim retry count in a row and the last known compaction result was skipped to consider using the OOM killer for assistance
> Both reclaim and compaction maintain their own retries counters as they > are targeting a different operation. Although the compaction really > depends on the reclaim to do some progress.
Yes. Looking at should_compact_retry() if the last known compaction result was skipped i.e. suggesting there was not enough order-0 pages to support compaction, so assistance is needed from reclaim (see __compaction_suitable()).
I noticed that the value of compaction_retries, compact_result and compact_priority was 0, COMPACT_SKIPPED and 1 i.e. COMPACT_PRIO_SYNC_LIGHT, respectively.
> OK, this sound unexpected as it indicates that the reclaim is able to > make a forward progress but compaction doesn't want to give up and keeps > retrying. Are you able to reproduce this or could you find out which > specific condition keeps compaction retrying? I would expect that it is > one of the 3 conditions before the max_retries is checked.
Unfortunately, I have been told it is not entirely reproducible. I suspect it is the following in should_compact_retry() - as I indicated above the last known value stored in compaction_retries was 0:
if (order > PAGE_ALLOC_COSTLY_ORDER) max_retries /= 4; if (*compaction_retries <= max_retries) { ret = true; goto out; }
Kind regards,
-- Aaron Tomlin
| |