diff options
| author | KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> | 2010-03-05 13:41:40 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-03-06 11:26:24 -0800 |
| commit | 34e55232e59f7b19050267a05ff1226e5cd122a5 (patch) | |
| tree | 6b94e776e87d2a2fe1ceca7c5606901575323900 /include | |
| parent | d559db086ff5be9bcc259e5aa50bf3d881eaf1d1 (diff) | |
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')
| -rw-r--r-- | include/linux/mm.h | 8 | ||||
| -rw-r--r-- | include/linux/mm_types.h | 6 | ||||
| -rw-r--r-- | include/linux/sched.h | 4 |
3 files changed, 12 insertions, 6 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 2124cdb2d1d..8e580c07d17 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -873,7 +873,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, /* * per-process(per-mm_struct) statistics. */ -#if USE_SPLIT_PTLOCKS +#if defined(SPLIT_RSS_COUNTING) /* * The mm counters are not protected by its page_table_lock, * so must be incremented atomically. @@ -883,10 +883,7 @@ static inline void set_mm_counter(struct mm_struct *mm, int member, long value) atomic_long_set(&mm->rss_stat.count[member], value); } -static inline unsigned long get_mm_counter(struct mm_struct *mm, int member) -{ - return (unsigned long)atomic_long_read(&mm->rss_stat.count[member]); -} +unsigned long get_mm_counter(struct mm_struct *mm, int member); static inline void add_mm_counter(struct mm_struct *mm, int member, long value) { @@ -974,6 +971,7 @@ static inline void setmax_mm_hiwater_rss(unsigned long *maxrss, *maxrss = hiwater_rss; } +void sync_mm_rss(struct task_struct *task, struct mm_struct *mm); /* * A callback you can register to apply pressure to ageable caches. diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index e1ca64be667..21861239ab0 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]; diff --git a/include/linux/sched.h b/include/linux/sched.h index cbeafa49a53..46c6f8d5dc0 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1220,7 +1220,9 @@ struct task_struct { struct plist_node pushable_tasks; struct mm_struct *mm, *active_mm; - +#if defined(SPLIT_RSS_COUNTING) + struct task_rss_stat rss_stat; +#endif /* task state */ int exit_state; int exit_code, exit_signal; |