• Mel Gorman's avatar
    mm: page_alloc: take the ALLOC_NO_WATERMARK check out of the fast path · 5dab2911
    Mel Gorman authored
    
    
    ALLOC_NO_WATERMARK is set in a few cases.  Always by kswapd, always for
    __GFP_MEMALLOC, sometimes for swap-over-nfs, tasks etc.  Each of these
    cases are relatively rare events but the ALLOC_NO_WATERMARK check is an
    unlikely branch in the fast path.  This patch moves the check out of the
    fast path and after it has been determined that the watermarks have not
    been met.  This helps the common fast path at the cost of making the slow
    path slower and hitting kswapd with a performance cost.  It's a reasonable
    tradeoff.
    Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
    Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
    Reviewed-by: default avatarRik van Riel <riel@redhat.com>
    Cc: Vlastimil Babka <vbabka@suse.cz>
    Cc: Jan Kara <jack@suse.cz>
    Cc: Michal Hocko <mhocko@suse.cz>
    Cc: Hugh Dickins <hughd@google.com>
    Cc: Dave Hansen <dave.hansen@intel.com>
    Cc: Theodore Ts'o <tytso@mit.edu>
    Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    5dab2911
page_alloc.c 183 KB