Messages in this thread Patch in this message | | | Date | Sat, 28 May 2022 19:48:06 -0500 | Subject | Re: [patch v5] mm: lru_cache_disable: replace work queue synchronization with synchronize_rcu | From | Michael Larabel <> |
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On 5/28/22 17:54, Michael Larabel wrote: > On 5/28/22 16:18, Andrew Morton wrote: >> On Thu, 28 Apr 2022 15:00:11 -0300 Marcelo Tosatti >> <mtosatti@redhat.com> wrote: >> >>> On Thu, Mar 31, 2022 at 03:52:45PM +0200, Borislav Petkov wrote: >>>> On Thu, Mar 10, 2022 at 10:22:12AM -0300, Marcelo Tosatti wrote: >>> ... >>> >>>> Someone pointed me at this: >>>> >>>> https://www.phoronix.com/scan.php?page=news_item&px=Linux-518-Stress-NUMA-Goes-Boom >>>> >>>> >>>> which says this one causes a performance regression with stress-ng's >>>> NUMA test... >>> Michael, >>> >>> This is probably do_migrate_pages that is taking too long due to >>> synchronize_rcu(). >>> >>> Switching to synchronize_rcu_expedited() should probably fix it... >>> Can you give it a try, please? >> I guess not. >> >> Is anyone else able to demonstrate a stress-ng performance regression >> due to ff042f4a9b0508? And if so, are they able to try Marcelo's >> one-liner? > > > Apologies I don't believe I got the email previously (or if it ended > up in spam or otherwise overlooked) so just noticed this thread now... > > I have the system around and will work on verifying it can reproduce > still and can then test the patch, should be able to get it tomorrow. > > Thanks and sorry about the delay. > > Michael > >
Had a chance to look at it today still. I was able to reproduce the regression still on that 5950X system going from v5.17 to v5.18 (using newer stress-ng benchmark and other system changes since the prior tests). Confirmed it also still showed slower as of today's Git.
I can confirm with Marcelo's patch below that the stress-ng NUMA performance is back to the v5.17 level of performance (actually, faster) and certainly not like what I was seeing on v5.18 or Git to this point.
So all seems to be good with that one-liner for the stress-ng NUMA test case. All the system details and results for those interested is documented @ https://openbenchmarking.org/result/2205284-PTS-NUMAREGR17 but basically amounts to:
Stress-NG 0.14 Test: NUMA Bogo Ops/s > Higher Is Better v5.17: 412.88 v5.18: 49.33 20220528 Git: 49.66 20220528 Git + sched-rcu-exped patch: 468.81
Apologies again about the delay / not seeing the email thread earlier.
Thanks,
Michael
Tested-by: Michael Larabel <Michael@MichaelLarabel.com>
> >> >>> diff --git a/mm/swap.c b/mm/swap.c >>> index bceff0cb559c..04a8bbf9817a 100644 >>> --- a/mm/swap.c >>> +++ b/mm/swap.c >>> @@ -879,7 +879,7 @@ void lru_cache_disable(void) >>> * lru_disable_count = 0 will have exited the critical >>> * section when synchronize_rcu() returns. >>> */ >>> - synchronize_rcu(); >>> + synchronize_rcu_expedited(); >>> #ifdef CONFIG_SMP >>> __lru_add_drain_all(true); >>> #else >>> >>>
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