• Alex Shi's avatar
    sched/numa: Load balance between remote nodes · 10717dcd
    Alex Shi authored
    Commit cb83b629 ("sched/numa: Rewrite the CONFIG_NUMA sched
    domain support") removed the NODE sched domain and started checking
    if the node distance in SLIT table is farther than REMOTE_DISTANCE,
    if so, it will lose the load balance chance at exec/fork/wake_affine
    points.
    
    But actually, even the node distance is farther than REMOTE_DISTANCE.
    
    Modern CPUs also has QPI like connections, which ensures that memory
    access is not too slow between nodes. So the above change in behavior
    on NUMA machine causes a performance regression on various benchmarks:
    hackbench, tbench, netperf, oltp, etc.
    
    This patch will recover the scheduler behavior to old mode on all my
    Intel platforms: NHM EP/EX, WSM EP, SNB EP/EP4S, and thus fixes the
    perfromance regressions. (all of them just have 2 kinds distance, 10, 21)
    Signed-off-by: default avatarAlex Shi <alex.shi@intel.com>
    Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
    Link: http://lkml.kernel.org/r/1338965571-9812-1-git-send-email-alex.shi@intel.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    10717dcd
core.c 197 KB