On Tue 06-09-16 15:52:54, Vlastimil Babka wrote:

After several people reported OOM's for order-2 allocations in 4.7 due to
Michal Hocko's OOM rework, he reverted the part that considered compaction
feedback [1] in the decisions to retry reclaim/compaction. This was to provide
a fix quickly for 4.8 rc and 4.7 stable series, while mmotm had an almost
complete solution that instead improved compaction reliability.

This series completes the mmotm solution and reintroduces the compaction
feedback into OOM decisions. The first two patches restore the state of mmotm
before the temporary solution was merged, the last patch should be the missing
piece for reliability. The third patch restricts the hardened compaction to
non-costly orders, since costly orders don't result in OOMs in the first place.

Some preliminary testing suggested that this approach should work, but I would
like to ask all who experienced the regression to please retest this. You will
need to apply this series on top of tag mmotm-2016-08-31-16-06 from the mmotm
git tree [2]. Thanks in advance!

We still do not ignore fragindex in the full priority. This part has
always been quite unclear to me so I cannot really tell whether that
makes any difference or not but just to be on the safe side I would
preffer to have _all_ the shortcuts out of the way in the highest
priority. It is true that this will cause COMPACT_NOT_SUITABLE_ZONE
so keep retrying but still a complication to understand the workflow.

What do you think?
-- 
Michal Hocko
SUSE Labs

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