• K
    mm: avoid false sharing of mm_counter · 34e55232
    KAMEZAWA Hiroyuki 提交于
    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: NKAMEZAWA 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: NAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
    34e55232
exec.c 45.2 KB