linux-kernel - Re: [RFC PATCH] sched: select_idle_core should select least utilized core

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Message-ID: <20170608195900.GA8337@worktop.programming.kicks-ass.net>
Date:   Thu, 8 Jun 2017 21:59:00 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Subhra Mazumdar <subhra.mazumdar@...cle.com>
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org
Subject: Re: [RFC PATCH] sched: select_idle_core should select least utilized
 core

On Thu, Jun 08, 2017 at 03:26:32PM -0400, Subhra Mazumdar wrote:
> Current select_idle_core tries to find a fully idle core and if it fails
> select_idle_cpu next returns any idle cpu in the llc domain. This is not optimal
> for architectures with many (more than 2) hyperthreads in a core. This patch
> changes select_idle_core to find the core with least number of busy
> hyperthreads and return an idle cpu in that core.

Yeah, I think not. That makes select_idle_siblings _vastly_ more
expensive.