Re: [rfc][patch] select_idle_sibling() inducing bouncing on westmere

[Mike Galbraith <efault@gmx.de>]

btw, numbers are intended to invoke: "Gee, wonder what if anything this
does to/for my favorite load" ;-)

On Wed, 2012-06-06 at 12:17 +0200, Mike Galbraith wrote: 
> On Thu, 2012-05-24 at 15:17 +0200, Peter Zijlstra wrote:
> 
> > Did you do you numbers with the distro NR_CPUS=4096 bloat?
> 
> 4 socket Westmere-EX 40 core box.. ouch^ouch. 
> 
> 3.0 has none of the below, 3.0x all, 3.0xx all but the ones commented
> out.  Most of the deltas are sibling avoidance, though throttle-nohz
> plays a role in 3.0 vs 3.0x, as does knob tweakery, though very very
> small for these particular tests.  The rest are ~meaningless.
> 
> sched-use-rt-nr_cpus_allowed-to-recover-select_task_rq-cycles.patch
> sched-set-skip_clock_update-when-yielding.patch
> sched-throttle-nohz.patch
> sched-Wrap-scheduler-p--cpus_allowed-access.patch
> sched-Avoid-SMT-siblings-in-select_idle_sibling-if-possible.patch
> sched-Clean-up-domain-traversal-in-select_idle_sibling.patch
> sched-Remove-rcu_read_lock-unlock-from-select_idle_sibling.patch
> sched-Fix-the-sched-group-node-allocation-for-SD_OVERLAP-domains.patch
> sched-domain-flags-proc-handler.patch
> # sched-tweak-select_idle_sibling.patch
> sched-tweak-knobs.patch
> # sched-ratelimit-affine-wakeup-migrations.patch
> 
> thench      1         2         4          8         16         32         64        128
> 3.0       225       451       911       1573       2723       3501      11189      13951
> 3.0x      299       603      1211       2418       4697       6847      11606      14557
> vs 3.0  1.328     1.337     1.329      1.537      1.724       1.955     1.037      1.043
> 
> 3.0xx      30        41       118        645       3769       6214      12233      14312
> vs 3.0x 0.100     0.067     0.097      0.266      0.802       0.907     1.054      0.983
>                                                                         hmmm 
> aim7 ~low load.. not saturating.
> 
> Benchmark       Version Machine Run Date
> AIM Multiuser Benchmark - Suite VII     "1.1"   3.0x      Jun  6 09:29:20 2012
> 
> Tasks   Jobs/Min        JTI     Real    CPU     Jobs/sec/task
> 64      26223.1         98      14.8    293.3   6.8289
> 
> Benchmark       Version Machine Run Date
> AIM Multiuser Benchmark - Suite VII     "1.1"   3.0xx     Jun  6 11:12:21 2012
> 
> Tasks   Jobs/Min        JTI     Real    CPU     Jobs/sec/task
> 64      18845.5         82      20.6    254.8   4.9077       vs 3.0x  0.718
> 
>