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

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Date:   Fri, 10 Feb 2023 09:41:14 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
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 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.