Messages in this thread | | | Date | Wed, 3 Aug 2022 12:37:55 -0700 | Subject | Re: [PATCH] sched/fair: no sync wakeup from interrupt context | From | Libo Chen <> |
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On 8/3/22 02:18, Ingo Molnar wrote: > * Libo Chen <libo.chen@oracle.com> wrote: > >> >> On 8/1/22 06:26, Ingo Molnar wrote: >>> * K Prateek Nayak <kprateek.nayak@amd.com> wrote: >>> >>>> Hello Libo and Peter, >>>> >>>> tl;dr >>>> >>>> - We observed a major regression with tbench when testing the latest tip >>>> sched/core at: >>>> commit 14b3f2d9ee8d "sched/fair: Disallow sync wakeup from interrupt context" >>>> Reason for the regression are the fewer affine wakeups that leaves the >>>> client farther away from the data it needs to consume next primed in the >>>> waker's LLC. >>>> Such regressions can be expected from tasks that use sockets to communicate >>>> significant amount of data especially on system with multiple LLCs. >>>> >>>> - Other benchmarks have a comparable behavior to the tip at previous commit >>>> commit : 91caa5ae2424 "sched/core: Fix the bug that task won't enqueue >>>> into core tree when update cookie" >>>> >>>> I'll leave more details below. >>> Mel Gorman also warned about this negative side-effect in: >>> >>> Subject: Re: [PATCH] sched/fair: no sync wakeup from interrupt context >>> Date: Fri, 15 Jul 2022 11:07:38 +0100 >>> Message-ID: <20220715100738.GD3493@suse.de> >>> >>> https://urldefense.com/v3/__https://lore.kernel.org/all/20220715100738.GD3493@suse.de/__;!!ACWV5N9M2RV99hQ!PQsIeuK0UwII-A0xS-B3plepNniNeyw14OJowT1cYL-tnuN99MkWfg9C8P60tVFFrnxj0NEanUmEkA$ >> ?? Mel was talking about a completely different thing, I brought up a >> different patch that I wanted to revert and Mel thought it would hurt other >> workloads which don't benefit from pulling but >> as you can see, tbench somehow benefits from it, at least according to one >> metric from one workload. > Yeah - but nevertheless the discussion with Mel was open-ended AFAICS, and > the 'major tbench regression' report by K Prateek Nayak above still stands > and needs to be investigated/understood, right? Oh yes, I have no issue with holding the patch back until the regression is fully understood. I was just a little confused on your reference to Mel's comments. Anyway, I will post my investigation soon.
Libo > Thanks, > > Ingo
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