Re: [External] : Re: [REGRESSION] sched/fair: Add lag based placement

[Joseph Salisbury <joseph.salisbury@oracle.com>]

On 11/13/24 13:19, Phil Auld wrote:
> Hi,
>
> On Wed, Nov 13, 2024 at 01:03:00PM -0500 Joseph Salisbury wrote:
>> Hello,
>>
>> During performance testing, we found a regression of ~9% performance with
>> the TPCC benchmark.   This performance regression was introduced in
>> v6.6-rc1.  After a bisect, the following commit was identified as the cause
>> of the regression:
>>
>> 86bfbb7ce4f6 ("sched/fair: Add lag based placement")
>>
>> I was hoping to get some feedback from the scheduler folks.  Do you think
>> gathering any additional data will help diagnose this issue?  Are there any
>> tunable options that can changed to see how performance is affected?
>>
> You can try turning off the PLACE_LAG sched feature:
>
>      echo NO_PLACE_LAG > /sys/kernel/debug/sched/features
>
> It's not what I'd call a tunable but it would allow you to test w/o it and
> see what it does.  It should allow you to switch back and forth easily for
> testing.
>
>
> Cheers,
> Phil
Thanks so much for the suggestion, Phil!  I will give that a try and 
report the results.
>
>> Thanks,
>>
>> Joe
>>
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