linux-kernel - Re: [RFC PATCH v8] sched: Fix performance regression introduced by mm

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Date:   Tue, 18 Apr 2023 14:24:39 -0400
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Aaron Lu <aaron.lu@...el.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, Olivier Dion <odion@...icios.com>,
        michael.christie@...cle.com
Subject: Re: [RFC PATCH v8] sched: Fix performance regression introduced by
 mm_cid

On 2023-04-18 12:01, Mathieu Desnoyers wrote:
> On 2023-04-18 07:21, Aaron Lu wrote:
>> On Mon, Apr 17, 2023 at 11:08:31AM -0400, Mathieu Desnoyers wrote:
>>> Introduce per-mm/cpu current concurrency id (mm_cid) to fix a PostgreSQL
>>> sysbench regression reported by Aaron Lu.
>>
>> For postgres_sysbench on SPR:
>> sched_mm_cid_migrate_to() is in the range of 0.1x% - 0.4x%, mm_cid_get()
>> is in the range of 0.1x% - 0.3x%. Other cid functions are pretty minor.
>>
>> For hackbench on SPR:
>> ched_mm_cid_migrate_to() is about 3%-4%, mm_cid_get() is about 7%-8%,
>> other cid functions are pretty minor.
> 
> It's a bit higher than I would have expected for hackbench.
> 
> Can you run with the attached schedstats patch applied and boot
> with schedstats=enable ? Let me know how the counters behave please,
> because I cannot reproduce anything unexpected on my machine.
> 

Also, just to confirm, do you still use this hackbench invocation ?

hackbench --pipe --threads -l 500000

Thanks,

Mathieu

> Thanks,
> 
> Mathieu
> 

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com