• Ingo Molnar's avatar
    sched: re-tune balancing · 9fcd18c9
    Ingo Molnar authored
    Impact: improve wakeup affinity on NUMA systems, tweak SMP systems
    
    Given the fixes+tweaks to the wakeup-buddy code, re-tweak the domain
    balancing defaults on NUMA and SMP systems.
    
    Turn on SD_WAKE_AFFINE which was off on x86 NUMA - there's no reason
    why we would not want to have wakeup affinity across nodes as well.
    (we already do this in the standard NUMA template.)
    
    lat_ctx on a NUMA box is particularly happy about this change:
    
    before:
    
     |   phoenix:~/l> ./lat_ctx -s 0 2
     |   "size=0k ovr=2.60
     |   2 5.70
    
    after:
    
     |   phoenix:~/l> ./lat_ctx -s 0 2
     |   "size=0k ovr=2.65
     |   2 2.07
    
    a 2.75x speedup.
    
    pipe-test is similarly happy about it too:
    
     |  phoenix:~/sched-tests> ./pipe-test
     |   18.26 usecs/loop.
     |   14.70 usecs/loop.
     |   14.38 usecs/loop.
     |   10.55 usecs/loop.              # +WAKE_AFFINE on domain0+domain1
     |   8.63 usecs/loop.
     |   8.59 usecs/loop.
     |   9.03 usecs/loop.
     |   8.94 usecs/loop.
     |   8.96 usecs/loop.
     |   8.63 usecs/loop.
    
    Also:
    
     - disable SD_BALANCE_NEWIDLE on NUMA and SMP domains (keep it for siblings)
     - enable SD_WAKE_BALANCE on SMP domains
    
    Sysbench+postgresql improves all around the board, quite significantly:
    
               .28-rc3-11474e2c  .28-rc3-11474e2c-tune
    -------------------------------------------------
        1:             571              688    +17.08%
        2:            1236             1206    -2.55%
        4:            2381             2642    +9.89%
        8:            4958             5164    +3.99%
       16:            9580             9574    -0.07%
       32:            7128             8118    +12.20%
       64:            7342             8266    +11.18%
      128:            7342             8064    +8.95%
      256:            7519             7884    +4.62%
      512:            7350             7731    +4.93%
    -------------------------------------------------
      SUM:           55412            59341    +6.62%
    
    So it's a win both for the runup portion, the peak area and the tail.
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    9fcd18c9
topology.h 6.71 KB