• Minchan Kim's avatar
    writeback: avoid unnecessary determine_dirtyable_memory call · 240c879f
    Minchan Kim authored
    I think determine_dirtyable_memory() is a rather costly function since it
    need many atomic reads for gathering zone/global page state.  But when we
    use vm_dirty_bytes && dirty_background_bytes, we don't need that costly
    calculation.
    
    This patch eliminates such unnecessary overhead.
    
    NOTE : newly added if condition might add overhead in normal path.
           But it should be _really_ small because anyway we need the
           access both vm_dirty_bytes and dirty_background_bytes so it is
           likely to hit the cache.
    
    [akpm@linux-foundation.org: fix used-uninitialised warning]
    Signed-off-by: default avatarMinchan Kim <minchan.kim@gmail.com>
    Cc: Wu Fengguang <fengguang.wu@intel.com>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    240c879f
page-writeback.c 39.1 KB