linux-kernel - Re: [PATCH v2] sched/topology: improve topology_span

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Message-ID: <Z2G_9WqiSdlv3ItV@swahl-home.5wahls.com>
Date: Tue, 17 Dec 2024 12:16:21 -0600
From: Steve Wahl <steve.wahl@....com>
To: Valentin Schneider <vschneid@...hat.com>
Cc: Steve Wahl <steve.wahl@....com>, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
        Mel Gorman <mgorman@...e.de>, linux-kernel@...r.kernel.org,
        K Prateek Nayak <kprateek.nayak@....com>,
        Vishal Chourasia <vishalc@...ux.ibm.com>, samir <samir@...ux.ibm.com>,
        Russ Anderson <rja@....com>, Dimitri Sivanich <sivanich@....com>
Subject: Re: [PATCH v2] sched/topology: improve topology_span_sane speed

On Mon, Dec 16, 2024 at 04:38:57PM +0100, Valentin Schneider wrote:
> 
> Hi,
> 
> Sorry it took me this long to get to this.
> 
...
> Per the previous comment, if you hinge the condition on @id itself,
> couldn't you "simplify" it as below?
> 
> 	if (cpumask_test_cpu(id, id_seen)) {
> 		/* First CPU has already been seen, ensure identical spans */
> 		if (!cpumask_equal(tl->mask(id), tl_cpu_mask))
> 			return false;
> 	} else {
> 		/* First CPU hasn't been seen before, ensure it's a completely new span */
> 		if (cpumask_intersects(tl_cpu_mask, covered))
> 			return false;
> 
> 		cpumask_or(covered, covered, tl_cpu_mask);
> 		cpumask_set_cpu(id, id_seen);
> 	}

After further evaluation, I wish to re-work this patch once again. I
ask that nobody consider merging this patch until I re-work it and
post v3.

Thanks,

--> Steve Wahl
-- 
Steve Wahl, Hewlett Packard Enterprise