• Johannes Weiner's avatar
    mm: page_alloc: exclude unreclaimable allocations from zone fairness policy · 73f038b8
    Johannes Weiner authored
    Dave Hansen noted a regression in a microbenchmark that loops around
    open() and close() on an 8-node NUMA machine and bisected it down to
    commit 81c0a2bb ("mm: page_alloc: fair zone allocator policy").
    That change forces the slab allocations of the file descriptor to spread
    out to all 8 nodes, causing remote references in the page allocator and
    slab.
    
    The round-robin policy is only there to provide fairness among memory
    allocations that are reclaimed involuntarily based on pressure in each
    zone.  It does not make sense to apply it to unreclaimable kernel
    allocations that are freed manually, in this case instantly after the
    allocation, and incur the remote reference costs twice for no reason.
    
    Only round-robin allocations that are usually freed through page reclaim
    or slab shrinking.
    
    Bisected by Dave Hansen.
    Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
    Cc: Dave Hansen <dave.hansen@intel.com>
    Cc: Mel Gorman <mgorman@suse.de>
    Reviewed-by: default avatarRik van Riel <riel@redhat.com>
    Cc: <stable@kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    73f038b8
page_alloc.c 179 KB