lkml.org 
[lkml]   [2012]   [Mar]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: sched: Avoid SMT siblings in select_idle_sibling() if possible
From
Date
On Thu, 2012-03-22 at 21:02 +0530, Srivatsa Vaddagiri wrote:
> Anyway, there are degradations as well, considering which I see
> several
> possibilities:
>
> 1. Do balance-on-wake for vcpu threads only.

Hell no ;-) we're not going to special case some threads over others.

> 2. Document tuning possibility to improve performance in virtualized
> environment:
> - Either via sched_domain flags (disable SD_WAKE_AFFINE
> at all levels and enable SD_BALANCE_WAKE at SMT/MC levels)

But domain flags are not exported -- except under SCHED_DEBUG and that
sysctl mess.. also SD_flags are not stable.

> - Or via a new sched_feat(BALANCE_WAKE) tunable

sched_feat() is not a stable ABI and shouldn't ever be used for anything
but debugging (hence it lives in debugfs and goes away if you disable
SCHED_DEBUG).


I would very much like more information on why things are a loss. Is it
really related to what cpu you pick, or is it the cost of doing the
balance thing?


\
 
 \ /
  Last update: 2012-03-26 10:33    [W:0.092 / U:1.440 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site