linux-kernel - Re: [PATCH -tip 09/32] sched/fair: Snapshot the min

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Message-ID: <2cb42831-5074-e0a9-9e2a-f2a880504026@linux.microsoft.com>
Date:   Mon, 23 Nov 2020 07:31:31 -0500
From:   Vineeth Pillai <viremana@...ux.microsoft.com>
To:     Balbir Singh <bsingharora@...il.com>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc:     Nishanth Aravamudan <naravamudan@...italocean.com>,
        Julien Desfossez <jdesfossez@...italocean.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Aaron Lu <aaron.lwe@...il.com>,
        Aubrey Li <aubrey.intel@...il.com>, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, mingo@...nel.org,
        torvalds@...ux-foundation.org, fweisbec@...il.com,
        keescook@...omium.org, kerrnel@...gle.com,
        Phil Auld <pauld@...hat.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>, vineeth@...byteword.org,
        Chen Yu <yu.c.chen@...el.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Agata Gruza <agata.gruza@...el.com>,
        Antonio Gomez Iglesias <antonio.gomez.iglesias@...el.com>,
        graf@...zon.com, konrad.wilk@...cle.com, dfaggioli@...e.com,
        pjt@...gle.com, rostedt@...dmis.org, derkling@...gle.com,
        benbjiang@...cent.com,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        James.Bottomley@...senpartnership.com, OWeisse@...ch.edu,
        Dhaval Giani <dhaval.giani@...cle.com>,
        Junaid Shahid <junaids@...gle.com>, jsbarnes@...gle.com,
        chris.hyser@...cle.com, Ben Segall <bsegall@...gle.com>,
        Josh Don <joshdon@...gle.com>, Hao Luo <haoluo@...gle.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Tim Chen <tim.c.chen@...el.com>
Subject: Re: [PATCH -tip 09/32] sched/fair: Snapshot the min_vruntime of CPUs
 on force idle

Hi Balbir,

On 11/22/20 6:44 AM, Balbir Singh wrote:
>
> This seems cumbersome, is there no way to track the min_vruntime via
> rq->core->min_vruntime?
Do you mean to have a core wide min_vruntime? We had a
similar approach from v3 to v7 and it had major issues which
broke the assumptions of cfs. There were some lengthy
discussions and Peter explained in-depth about the issues:

https://lwn.net/ml/linux-kernel/20200506143506.GH5298@hirez.programming.kicks-ass.net/
https://lwn.net/ml/linux-kernel/20200515103844.GG2978@hirez.programming.kicks-ass.net/

Thanks,
Vineeth