lkml.org 
[lkml]   [2014]   [Oct]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: Slowdown due to threads bouncing between HT cores
Date
"Steinar H. Gunderson" <sgunderson@bigfoot.com> writes:
>
> So, benchmark:
>
> - Default: 13266 kN/sec
> - Change from ondemand to performance on all cores: 14600 kN/sec
> - taskset -c 0-19 (locking affinity to only one set of hyperthreads):
> 17512 kN/sec

iirc the main reasons for unbound threads migrating away are:

- something else gets scheduled on these logical CPUs, so
the scheduler tries to balance to run queue lengths

You could check that with perf timechart or perf sched record/map
or kernelshark.

- there is some IO or communication which causes wakeup affinity.

You could try disabling WAKEUP_PREEMPTION or NEXT_BUDDY in
/sys/kernel/debug/sched_features

-Andi
--
ak@linux.intel.com -- Speaking for myself only


\
 
 \ /
  Last update: 2014-10-04 16:21    [W:0.530 / U:0.004 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site