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From: Peter Zijlstra <peterz@infradead.org>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@surriel.com>, Ingo Molnar <mingo@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Mel Gorman <mgorman@techsingularity.net>,
	Thomas Gleixner <tglx@linutronix.de>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Michael Neuling <mikey@neuling.org>,
	Gautham R Shenoy <ego@linux.vnet.ibm.com>,
	Parth Shah <parth@linux.ibm.com>
Subject: Re: [PATCH] sched/fair: Prefer idle CPU to cache affinity
Date: Tue, 2 Mar 2021 10:10:32 +0100	[thread overview]
Message-ID: <YD4BCDlxvn7ub+9U@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210302073946.GL2028034@linux.vnet.ibm.com>

On Tue, Mar 02, 2021 at 01:09:46PM +0530, Srikar Dronamraju wrote:
> > Oh, could be, I didn't grep :/ We could have core code keep track of the
> > smt count I suppose.
> 
> Could we use cpumask_weight(cpu_smt_mask(this_cpu)) instead?

cpumask_weight() is potentially super expensive. With CPUMASK_OFFSTACK
you get at least one more cache miss and then the bitmap might be really
long.

Best to compute the results once and use it later.

  reply	other threads:[~2021-03-02  9:49 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-26 16:40 [PATCH] sched/fair: Prefer idle CPU to cache affinity Srikar Dronamraju
2021-02-27 19:56 ` Rik van Riel
2021-03-01 13:37   ` Srikar Dronamraju
2021-03-01 15:44   ` Peter Zijlstra
2021-03-01 17:06     ` Srikar Dronamraju
2021-03-01 17:18       ` Peter Zijlstra
2021-03-02  7:39         ` Srikar Dronamraju
2021-03-02  9:10           ` Peter Zijlstra [this message]
2021-03-02 10:05             ` Srikar Dronamraju
2021-03-01 15:40 ` Peter Zijlstra
2021-03-01 17:08   ` Srikar Dronamraju
2021-03-02  9:53 ` Dietmar Eggemann
2021-03-02 10:04   ` Srikar Dronamraju
2021-03-08 13:52 ` Vincent Guittot
2021-03-10  5:52   ` Srikar Dronamraju
2021-03-10 15:37     ` Vincent Guittot

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