linux-kernel - Re: [PATCH v3 04/10] sched/fair: Let low-priority cores help high-priority busy SMT cores

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Message-ID: <20230210130556.GA8447@ranerica-svr.sc.intel.com>
Date:   Fri, 10 Feb 2023 05:05:56 -0800
From:   Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Ricardo Neri <ricardo.neri@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Len Brown <len.brown@...el.com>, Mel Gorman <mgorman@...e.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Ionela Voinescu <ionela.voinescu@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, "Tim C . Chen" <tim.c.chen@...el.com>
Subject: Re: [PATCH v3 04/10] sched/fair: Let low-priority cores help
 high-priority busy SMT cores

On Fri, Feb 10, 2023 at 09:41:14AM +0100, Peter Zijlstra wrote:
> On Thu, Feb 09, 2023 at 04:43:33PM -0800, Ricardo Neri wrote:
> > On Thu, Feb 09, 2023 at 12:53:41PM +0100, Peter Zijlstra wrote:
> > > On Wed, Feb 08, 2023 at 08:56:32AM +0100, Vincent Guittot wrote:
> > > 
> > > > > +                       if (env->sd->flags & SD_SHARE_CPUCAPACITY ||
> > > > > +                           (!(env->sd->flags & SD_SHARE_CPUCAPACITY) && is_core_idle(i)))
> > > > 
> > > > This 2nd if could be merged with the upper one
> > > 
> > > Wasn't this exact same condition used in the previous patch as well?
> > > Does it wants to be a helper perhaps?
> > 
> > Patch 3 focuses on the destination CPU: make sure that it and its SMT
> > siblings are idle before attempting to do asym_packing balance.
> > 
> > This patch focuses on the busiest group: if the busiest group is an SMT
> > core with more than one busy sibling, help it even if it has higher
> > priority.
> 
> Yeah, so? If its a recurring expression a helper never hurts.

Ah! I get your point now. You meant a helper function. Thank you for the
clarification.

Sure! I can add this helper function.