There were some reports about processes getting stalled for very long
periods of time in compaction. The bulk of this problem turned out
to be due to an accounting error wherby the isolated count could go
negative but only noticed by UP builds.
This series is the useful patches (not all mine) that came out of
the related discussions that are in mainline for 3.0.
Patch 1 is the primary fix for a problem where the isolated count
could go negative on one zone and remain elevated on another.
Patch 2 notes that the linear scanner in vmscan.c cannot safely
use page_count because it could be scanning a tail page.
Patch 3 fixes a problem whereby asynchronous callers to compaction
can still stall in too_many_isolated when it should just fail
the allocation.
It was asked that testers reverify this actually fixed the problem and
based on https://lkml.org/lkml/2011/7/17/10, the patches are required.
mm/compaction.c | 42 ++++++++++++++++++++++++++++++++++++------
mm/vmscan.c | 16 ++++++++++++++--
2 files changed, 50 insertions(+), 8 deletions(-)
--
1.7.3.4
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