linux-kernel - Re: [PATCH -tip 15/32] sched: Improve snapshotting of min

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Message-ID: <20201124104142.GX3021@hirez.programming.kicks-ass.net>
Date:   Tue, 24 Nov 2020 11:41:42 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc:     Nishanth Aravamudan <naravamudan@...italocean.com>,
        Julien Desfossez <jdesfossez@...italocean.com>,
        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>,
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        Dhaval Giani <dhaval.giani@...cle.com>,
        Junaid Shahid <junaids@...gle.com>, jsbarnes@...gle.com,
        chris.hyser@...cle.com, Ben Segall <bsegall@...gle.com>,
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        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 15/32] sched: Improve snapshotting of min_vruntime
 for CGroups

On Tue, Nov 17, 2020 at 06:19:45PM -0500, Joel Fernandes (Google) wrote:
> +static void se_fi_update(struct sched_entity *se, unsigned int fi_seq, bool forceidle)
>  {
> -	bool samecpu = task_cpu(a) == task_cpu(b);
> +	bool root = true;
> +	long old, new;

My compiler was not impressed by all those variable definitions.

> +
> +	for_each_sched_entity(se) {
> +		struct cfs_rq *cfs_rq = cfs_rq_of(se);
> +
> +		if (forceidle) {
> +			if (cfs_rq->forceidle_seq == fi_seq)
> +				break;
> +			cfs_rq->forceidle_seq = fi_seq;
> +		}
> +
> +		cfs_rq->min_vruntime_fi = cfs_rq->min_vruntime;
> +	}
> +}