linux-kernel - Re: [RFC] Perfomance varies according to sysctl_sched_migration

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Message-ID: <YUCHwYo525+/98wq@hirez.programming.kicks-ass.net>
Date:   Tue, 14 Sep 2021 13:30:09 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Yicong Yang <yangyicong@...ilicon.com>
Cc:     mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, 21cnbao@...il.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>,
        prime.zeng@...wei.com,
        "guodong.xu@...aro.org" <guodong.xu@...aro.org>
Subject: Re: [RFC] Perfomance varies according to sysctl_sched_migration_cost

On Tue, Sep 14, 2021 at 03:27:09PM +0800, Yicong Yang wrote:
> 2. The ABI now has been removed from sysctl and moved to debugfs. As tuning this can improve the performance
>    of some workloads on some platforms, maybe it's better to make it a formal sysctl again with docs?

It never was an ABI, there is nothing to restore. It has always been
CONFIG_SCHED_DEBUG.

I'm open to topology based improvements to the code, but I don't think
user tunables are a good way.