linux-kernel - Re: [PATCH -tip 01/32] sched: Wrap rq::lock access

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Date:   Sun, 22 Nov 2020 19:52:00 +1100
From:   Balbir Singh <bsingharora@...il.com>
To:     Joel Fernandes <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>,
        Vineeth Pillai <viremana@...ux.microsoft.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 01/32] sched: Wrap rq::lock access

On Fri, Nov 20, 2020 at 11:55:22AM -0500, Joel Fernandes wrote:
> On Fri, Nov 20, 2020 at 10:31:39AM +1100, Singh, Balbir wrote:
> > On 18/11/20 10:19 am, Joel Fernandes (Google) wrote:
> > > From: Peter Zijlstra <peterz@...radead.org>
> > > 
> > > In preparation of playing games with rq->lock, abstract the thing
> > > using an accessor.
> > > 
> > 
> > Could you clarify games? I presume the intention is to redefine the scope
> > of the lock based on whether core sched is enabled or not? I presume patch
> > 4/32 has the details.
> 
> Your line wrapping broke, I fixed it.
>

Sorry, I've been using thunderbird from time to time and even though
I set the options specified in the Documentation (email-clients), it's
not working as expected.

> That is in fact the game. By wrapping it, the nature of the locking is
> dynamic based on whether core sched is enabled or not (both statically and
> dynamically).
>

My point was that the word game does not do justice to the change, some
details around how this abstractions helps based on the (re)definition of rq
with coresched might help.

Balbir Singh.