Re: CFS review

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Ingo Molnar wrote:
* Al Boldi <[email protected]> wrote:

ok. I think i might finally have found the bug causing this. Could you try the fix below, does your webserver thread-startup test work any better?
It seems to help somewhat, but the problem is still visible. Even v20.3 on 2.6.22.5 didn't help.

It does look related to ia-boosting, so I turned off __update_curr like Roman mentioned, which had an enormous smoothing effect, but then nice levels completely break down and lockup the system.

you can turn sleeper-fairness off via:

   echo 28 > /proc/sys/kernel/sched_features

another thing to try would be:

   echo 12 > /proc/sys/kernel/sched_features

14, and drop the granularity to 500000.

(that's the new-task penalty turned off.)

Another thing to try would be to edit this:

        if (sysctl_sched_features & SCHED_FEAT_START_DEBIT)
                p->se.wait_runtime = -(sched_granularity(cfs_rq) / 2);

to:

        if (sysctl_sched_features & SCHED_FEAT_START_DEBIT)
                p->se.wait_runtime = -(sched_granularity(cfs_rq);

and could you also check 20.4 on 2.6.22.5 perhaps, or very latest -git? (Peter has experienced smaller spikes with that.)

	Ingo


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Bill Davidsen <[email protected]>
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