lkml.org 
[lkml]   [2016]   [May]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: sched: tweak select_idle_sibling to look for idle threads
    From
    Date
    On Sat, 2016-04-30 at 14:47 +0200, Peter Zijlstra wrote:
    > On Sat, Apr 09, 2016 at 03:05:54PM -0400, Chris Mason wrote:
    > > select_task_rq_fair() can leave cpu utilization a little lumpy,
    > > especially as the workload ramps up to the maximum capacity of the
    > > machine. The end result can be high p99 response times as apps
    > > wait to get scheduled, even when boxes are mostly idle.
    > >
    > > I wrote schbench to try and measure this:
    > >
    > > git://git.kernel.org/pub/scm/linux/kernel/git/mason/schbench.git
    >
    > Can you guys have a play with this; I think one and two node tbench are
    > good, but I seem to be getting significant run to run variance on that,
    > so maybe I'm not doing it right.

    Nah, tbench is just variance prone. It got dinged up at clients=cores
    on my desktop box, on 4 sockets the high end got seriously dinged up.

    tbench

    1 x i4790
    master avg
    1 714 684 688 695 1.000
    2 1260 1234 1284 1259 1.000
    4 2238 2301 2286 2275 1.000
    8 3388 3418 3396 3400 1.000

    masterx
    1 690 701 701 697 1.002
    2 1287 1332 1235 1284 1.019
    4 2014 2006 1999 2006 0.881
    8 3388 3385 3404 3392 0.997

    4 x E7-8890
    master avg
    1 524 524 523 523 1.000
    2 1049 1053 1045 1049 1.000
    4 2064 2081 2091 2078 1.000
    8 3737 3813 3746 3765 1.000
    16 7129 7028 7082 7079 1.000
    32 13718 13730 13578 13675 1.000
    64 21397 21435 21519 21450 1.000
    128 39846 38397 39026 39089 1.000
    256 59509 59797 59344 59550 1.000

    masterx avg
    1 505 507 501 504 0.963 1.000
    2 1036 1027 1039 1034 0.985 1.000
    4 1977 2001 1992 1990 0.957 1.000
    8 3734 3802 3778 3771 1.001 1.000
    16 7124 7079 7071 7091 1.001 1.000
    32 13549 13758 13364 13557 0.991 1.000
    64 21975 22161 22100 22078 1.029 1.000
    128 23066 23044 23028 23046 0.589 1.000
    256 29905 29630 30753 30096 0.505 1.000

    masterx NO_IDLE_CORE avg
    1 500 521 502 507 0.969 1.005
    2 1012 996 1043 1017 0.969 0.983
    4 1988 1992 1995 1991 0.958 1.000
    8 3834 3758 3671 3754 0.997 0.995
    16 7160 7206 7168 7178 1.013 1.012
    32 13788 13773 13672 13744 1.005 1.013
    64 21771 21845 21826 21814 1.016 0.988
    128 23248 23136 23133 23172 0.592 1.005
    256 28683 30013 31850 30182 0.506 1.002

    \
     
     \ /
      Last update: 2016-05-01 09:21    [W:18.762 / U:0.032 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site