Ingo Molnar wrote:
> * Balbir Singh <[email protected]> wrote:
>
>> Hi, Ingo,
>>
>> I missed commit 75d4ef16a6aa84f708188bada182315f80aab6fa
>> "sched: fix delay accounting performance regression"
>>
>> Without these changes, I find that delay accounting does
>> not work as expected, I see zeros in the field for virtual,delay
>> and count(s).
>>
>> CPU count real total virtual total delay total
>> 0 535861848 0 0
>>
>>
>> This breaks existing delay accounting behaviour.
>>
>> Am I missing something?
>
> delay accounting was causing context-switch slowdown because it called
> sched_clock() explicitly - but indeed my fix to that is wrong ...
>
> how about reverting the change but also using rq->clock instead of
> sched_clock()?
Hmm... I think that might work, I find that schedule() calls
__update_rq_clock() which in turn calls sched_clock(), so it
might be a worthwhile optimization.
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
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