Re: [PATCH 3/4] mm: memory-failure: Fix isolated page count during memory failure

On Tue 07-06-11 16:07:04, Mel Gorman wrote:

From: Minchan Kim <redacted>

From: Minchan Kim <redacted>

Pages isolated for migration are accounted with the vmstat counters
NR_ISOLATE_[ANON|FILE]. Callers of migrate_pages() are expected to
increment these counters when pages are isolated from the LRU. Once
the pages have been migrated, they are put back on the LRU or freed
and the isolated count is decremented.

Aren't we missing this in compact_zone as well? AFAICS there is no
accounting done after we isolate pages from LRU? Or am I missing
something?

Memory failure is not properly accounting for pages it isolates
causing the NR_ISOLATED counters to be negative. On SMP builds,
this goes unnoticed as negative counters are treated as 0 due to
expected per-cpu drift. On UP builds, the counter is treated by
too_many_isolated() as a large value causing processes to enter D
state during page reclaim or compaction. This patch accounts for
pages isolated by memory failure correctly.

[mgorman@suse.de: Updated changelog]
Signed-off-by: Minchan Kim <redacted>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Andrea Arcangeli <redacted>

Reviewed-by: Michal Hocko <redacted>

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

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