mm/page_alloc: bail out on fatal signal during reclaim/compaction retry attempt

A customer experienced a low-memory situation and decided to issue a
SIGKILL (i.e.  a fatal signal).  Instead of promptly terminating as one
would expect, the aforementioned task remained unresponsive.

Further investigation indicated that the task was "stuck" in the
reclaim/compaction retry loop.  Now, it does not make sense to retry
compaction when a fatal signal is pending.

In the context of try_to_compact_pages(), indeed COMPACT_SKIPPED can be
returned; albeit, not every zone, on the zone list, would be considered in
the case a fatal signal is found to be pending.  Yet, in
should_compact_retry(), given the last known compaction result, each zone,
on the zone list, can be considered/or checked (see
compaction_zonelist_suitable()).  For example, if a zone was found to
succeed, then reclaim/compaction would be tried again (notwithstanding the
above).

This patch ensures that compaction is not needlessly retried irrespective
of the last known compaction result e.g.  if it was skipped, in the
unlikely case a fatal signal is found pending.  So, OOM is at least
attempted.

Link: https://lkml.kernel.org/r/20210520142901.3371299-1-atomlin@redhat.com
Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Aaron Tomlin 2021-06-28 19:41:10 -07:00 committed by Linus Torvalds
parent d2f07ec052
commit 691d949728
1 changed files with 3 additions and 0 deletions

View File

@ -4251,6 +4251,9 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
if (!order)
return false;
if (fatal_signal_pending(current))
return false;
if (compaction_made_progress(compact_result))
(*compaction_retries)++;