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* [REGRESSION][v6.17-rc1]sched/fair: Bump sd->max_newidle_lb_cost when newidle balance fails
@ 2025-10-06 20:23 Joseph Salisbury
  2025-10-06 21:23 ` Chris Mason
  0 siblings, 1 reply; 17+ messages in thread
From: Joseph Salisbury @ 2025-10-06 20:23 UTC (permalink / raw)
  To: clm
  Cc: Peter Zijlstra, Vincent Guittot, Juri Lelli, Ingo Molnar,
	dietmar.eggemann, Steven Rostedt, bsegall, mgorman, vschneid,
	LKML

Hi Chris,

During testing, we are seeing a ~6% performance regression with the 
upstream stable v6.12.43 kernel (And Oracle UEK 
6.12.0-104.43.4.el9uek.x86_64 kernel) when running the Phoronix 
pts/apache benchmark with 100 concurrent requests [0].  The regression 
is seen with the following hardware:

PROCESSOR: Intel Xeon Platinum 8167M Core Count: 8 Thread Count: 16 
Extensions: SSE 4.2 + AVX512CD + AVX2 + AVX + RDRAND + FSGSBASE Cache 
Size: 16 MB Microcode: 0x1 Core Family: Cascade Lake

After performing a bisect, we found that the performance regression was 
introduced by the following commit:

Stable v6.12.43: fc4289233e4b ("sched/fair: Bump sd->max_newidle_lb_cost 
when newidle balance fails")
Mainline v6.17-rc1: 155213a2aed4 ("sched/fair: Bump 
sd->max_newidle_lb_cost when newidle balance fails")

Reverting this commit causes the performance regression to not exist.

I was hoping to get your feedback, since you are the patch author.  Do 
you think gathering any additional data will help diagnose this issue?

Thanks,

Joe


[0]https://openbenchmarking.org/test/pts/apache-3.0.0


^ permalink raw reply	[flat|nested] 17+ messages in thread

end of thread, other threads:[~2025-11-04 18:12 UTC | newest]

Thread overview: 17+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-10-06 20:23 [REGRESSION][v6.17-rc1]sched/fair: Bump sd->max_newidle_lb_cost when newidle balance fails Joseph Salisbury
2025-10-06 21:23 ` Chris Mason
2025-10-07 11:34   ` Peter Zijlstra
2025-10-10  1:04     ` [External] : " Joseph Salisbury
2025-10-10 17:09       ` Peter Zijlstra
2025-10-17 17:01         ` Joseph Salisbury
2025-10-30  7:29           ` Adam Li
2025-10-31 21:16             ` [External] : " Joseph Salisbury
2025-11-04 18:11             ` Joseph Salisbury
2025-10-30  7:22         ` Adam Li
2025-10-30  9:30           ` Peter Zijlstra
2025-10-30 20:53             ` Dietmar Eggemann
2025-10-31  2:46             ` Adam Li
2025-10-10  1:14     ` Joseph Salisbury
2025-10-07 20:22   ` [External] : " Joseph Salisbury
2025-10-10 13:09   ` Hazem Mohamed Abuelfotoh
2025-10-27 18:36   ` Josh Don

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