Re: balance storm

Mike Galbraith
2014-05-26T07:56:31Z

On Mon, 2014-05-26 at 11:04 +0800, Libo Chen wrote:
> hi,
> my box has 16 cpu (E5-2658,8 core, 2 thread per core), i did a test on
> 3.4.24stable, startup 50 same process, every process is sample:
>
> #include <unistd.h>
>
> int main()
> {
> for (;;)
> {
> unsigned int i = 0;
> while (i< 100){
> i++;
> }
> usleep(100);
> }
>
> return 0;
> }
>
> the result is process uses 15% cpu time, perf tool shows 70w migrations in 5 second.

My 8 socket 64 core DL980 running 256 copies (3.14-rt5) munches ~4%/copy
per top, and does roughly 1 sh*tload migrations, nano-work loop or not.
Turn SD_SHARE_PKG_RESOURCES off at MC (not a noop here), and consumption
drops to ~2%/copy, and migrations ('course) mostly go away.

vogelweide:/abuild/mike/:[0]# perf stat -a -e sched:sched_migrate_task -- sleep 5

Performance counter stats for 'system wide':

3108 sched:sched_migrate_task

5.001367910 seconds time elapsed

(turns SD_SHARE_PKG_RESOURCES back on)

vogelweide:/abuild/mike/:[0]# perf stat -a -e sched:sched_migrate_task -- sleep 5

Performance counter stats for 'system wide':

4182334 sched:sched_migrate_task

5.001365023 seconds time elapsed

vogelweide:/abuild/mike/:[0]#