[RFC 00/13] make direct compaction more deterministic

Vlastimil Babka
2016-05-10T07:37:10Z

This is mostly a followup to Michal's oom detection rework, which highlighted
the need for direct compaction to provide better feedback in reclaim/compaction
loop, so that it can reliably recognize when compaction cannot make further
progress, and allocation should invoke OOM killer or fail. We've discussed
this at LSF/MM [1] where I proposed expanding the async/sync migration mode
used in compaction to more general "priorities". This patchset adds one new
priority that just overrides all the heuristics and makes compaction fully
scan all zones. I don't currently think that we need more fine-grained
priorities, but we'll see. Other than that there's some smaller fixes and
cleanups, mainly related to the THP-specific hacks.

Testing/evaluation is pending, but I'm posting it now with hope to help the
discussions around oom detection rework. I also hope for testing the near-OOM
conditions, and the new priority level should also help hugetlbfs allocations
since they use __GFP_RETRY, and it has already been reported that ignoring
compaction heuristics helps these allocations.

The series is based on mmotm git [2] tag mmotm-2016-04-27-15-21-14.
First one needs to git revert the commit 69340d225e8d ("mm: use compaction
feedback for thp backoff conditions") which already happened in mmots.

[1] https://lwn.net/Articles/684611/
[2] git://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git

Hugh Dickins (1):
mm, compaction: don't isolate PageWriteback pages in
MIGRATE_SYNC_LIGHT mode

Vlastimil Babka (12):
mm, page_alloc: set alloc_flags only once in slowpath
mm, page_alloc: don't retry initial attempt in slowpath
mm, page_alloc: restructure direct compaction handling in slowpath
mm, page_alloc: make THP-specific decisions more generic
mm, thp: remove __GFP_NORETRY from khugepaged and madvised allocations
mm, compaction: introduce direct compaction priority
mm, compaction: simplify contended compaction handling
mm, compaction: make whole_zone flag ignore cached scanner positions
mm, compaction: cleanup unused functions
mm, compaction: add the ultimate direct compaction priority
mm, compaction: more reliably increase direct compaction priority
mm, compaction: fix and improve watermark handling

include/linux/compaction.h | 32 +++----
include/linux/gfp.h | 3 +-
include/linux/mm.h | 2 +-
mm/compaction.c | 196 +++++++++++++++-------------------------
mm/huge_memory.c | 8 +-
mm/internal.h | 10 +--
mm/page_alloc.c | 220 +++++++++++++++++++++------------------------
mm/page_isolation.c | 2 +-
8 files changed, 196 insertions(+), 277 deletions(-)

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2.8.2