From: Libo Chen <libo.chen@oracle.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>,
peterz@infradead.org, vincent.guittot@linaro.org,
mgorman@suse.de, tim.c.chen@linux.intel.com, 21cnbao@gmail.com,
dietmar.eggemann@arm.com, linux-kernel@vger.kernel.org,
tglx@linutronix.de
Subject: Re: [PATCH] sched/fair: no sync wakeup from interrupt context
Date: Wed, 3 Aug 2022 12:37:55 -0700 [thread overview]
Message-ID: <a9d666ae-0aa4-d79e-aac2-02573577b530@oracle.com> (raw)
In-Reply-To: <Yuo9Y4KvQQvvLC/r@gmail.com>
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
next prev parent reply other threads:[~2022-08-03 19:38 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-11 22:47 [PATCH] sched/fair: no sync wakeup from interrupt context Libo Chen
2022-07-13 16:40 ` Tim Chen
[not found] ` <0917f479-b6aa-19de-3d6a-6fd422df4d21@oracle.com>
2022-07-13 19:34 ` Libo Chen
2022-07-13 20:51 ` Tim Chen
2022-07-13 21:37 ` Libo Chen
2022-07-14 14:18 ` Mel Gorman
2022-07-14 20:21 ` Libo Chen
2022-07-15 10:07 ` Mel Gorman
2022-07-14 11:26 ` Peter Zijlstra
2022-07-14 11:35 ` Peter Zijlstra
2022-07-14 18:18 ` Libo Chen
2022-07-21 8:44 ` [tip: sched/core] sched/fair: Disallow " tip-bot2 for Libo Chen
2022-07-29 4:47 ` [PATCH] sched/fair: no " K Prateek Nayak
2022-08-01 13:26 ` Ingo Molnar
2022-08-01 14:59 ` Libo Chen
2022-08-03 9:18 ` Ingo Molnar
2022-08-03 19:37 ` Libo Chen [this message]
2022-08-04 8:55 ` Ingo Molnar
2022-08-04 9:51 ` Mel Gorman
2022-08-01 14:57 ` Libo Chen
2022-08-02 4:40 ` K Prateek Nayak
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