linux-kernel - Re: [PATCH v2] sched/fair: Fix clearing of has_idle

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Message-ID: <YJugQn6XNGF9/c3h@hirez.programming.kicks-ass.net>
Date:   Wed, 12 May 2021 11:30:42 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
Cc:     Mel Gorman <mgorman@...hsingularity.net>,
        Ingo Molnar <mingo@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] sched/fair: Fix clearing of has_idle_cores flag

On Tue, May 11, 2021 at 08:46:09PM +0530, Gautham R. Shenoy wrote:
> From: "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
> 
> In commit 9fe1f127b913 ("sched/fair: Merge select_idle_core/cpu()"),
> in select_idle_cpu(), we check if an idle core is present in the LLC
> of the target CPU via the flag "has_idle_cores". We look for the idle
> core in select_idle_cores(). If select_idle_cores() isn't able to find
> an idle core/CPU, we need to unset the has_idle_cores flag in the LLC
> of the target to prevent other CPUs from going down this route.
> 
> However, the current code is unsetting it in the LLC of the current
> CPU instead of the target CPU. This patch fixes this issue.
> 
> Fixes: Commit 9fe1f127b913 ("sched/fair: Merge select_idle_core/cpu()")
> Acked-by: Mel Gorman <mgorman@...hsingularity.net>
> Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>
> Reviewed-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> Signed-off-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>

Thanks!