On 08/26/2014 09:30 AM, Minchan Kim wrote:
Recently, I saw several reports that high order allocation failed
although there were many freeable pages but it's hard to reproduce
so asking them to reproduce the problem several time is really painful.
A culprit I doubt is compaction deferring logic which prevent
compaction for a while so high order allocation could be fail.
Could be that, but also the non-determinism of watermark checking, where
compaction thinks allocation should succeed, but in the end it won't.
It would be more clear if we can see the stat which can show
current zone's compaction deferred state when allocatil fail.
It's a RFC and never test it. I just get an idea with
handling another strange high order allocation fail.
Any comments are welcome.
It's quite large patch. Maybe it could be much simpler if you did not
print just true/false but:
1) true/false based on zone->compact_considered < defer_limit, ignoring
zone->compact_order_failed
2) zone->compact_order_failed value itself
Then you wouldn't need to pass the allocation order around like you do.
The "allocation failed" message tells you the order which was attempted,
and then it's easy for the user to compare with the reported
zone->compact_order_failed and decide if the defer status actually
applies or not.
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