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author | KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> | 2010-03-05 13:41:40 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-03-06 11:26:24 -0800 |
commit | 34e55232e59f7b19050267a05ff1226e5cd122a5 (patch) | |
tree | 6b94e776e87d2a2fe1ceca7c5606901575323900 /include/linux/mm_types.h | |
parent | d559db086ff5be9bcc259e5aa50bf3d881eaf1d1 (diff) | |
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mm: avoid false sharing of mm_counter
Considering the nature of per mm stats, it's the shared object among
threads and can be a cache-miss point in the page fault path.
This patch adds per-thread cache for mm_counter. RSS value will be
counted into a struct in task_struct and synchronized with mm's one at
events.
Now, in this patch, the event is the number of calls to handle_mm_fault.
Per-thread value is added to mm at each 64 calls.
rough estimation with small benchmark on parallel thread (2threads) shows
[before]
4.5 cache-miss/faults
[after]
4.0 cache-miss/faults
Anyway, the most contended object is mmap_sem if the number of threads grows.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/mm_types.h')
-rw-r--r-- | include/linux/mm_types.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index e1ca64b..2186123 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -202,9 +202,15 @@ enum { }; #if USE_SPLIT_PTLOCKS +#define SPLIT_RSS_COUNTING struct mm_rss_stat { atomic_long_t count[NR_MM_COUNTERS]; }; +/* per-thread cached information, */ +struct task_rss_stat { + int events; /* for synchronization threshold */ + int count[NR_MM_COUNTERS]; +}; #else /* !USE_SPLIT_PTLOCKS */ struct mm_rss_stat { unsigned long count[NR_MM_COUNTERS]; |