Messages in this thread | | | Date | Mon, 28 Jan 2008 17:57:49 +0100 | From | "Guillaume Chazarain" <> | Subject | Re: High wake up latencies with FAIR_USER_SCHED |
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Hi Srivatsa,
On Jan 28, 2008 3:31 AM, Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> wrote: > Given that sysctl_sched_wakeup_granularity is set to 10ms by default, > this doesn't sound abnormal.
Indeed, by lowering sched_wakeup_granularity I get much better latencies, but lowering sched_latency seems to be more effective.
> NEW_FAIR_SLEEPERS feature gives credit for sleeping only to tasks and > not group-level entities. With the patch attached, I could see that wakeup > latencies with FAIR_USER_SCHED are restored to the same level as > !FAIR_USER_SCHED.
Thanks for the patch, it works perfectly.
> However I am not sure whether that is the way to go. We want to let one group of > tasks running as much as possible until the fairness/wakeup-latency threshold is > exceeded. If someone does want better wakeup latencies between groups too, they > can always tune sysctl_sched_wakeup_granularity.
Having an inconsistency here between FAIR_USER_SCHED and !FAIR_USER_SCHED sounds strange, but Ingo took the patch, so I'm happy :-)
Thanks for the replies.
-- Guillaume
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