linux-kernel - Re: [PATCH 4/4] sched/fair: Use a recently used CPU as an idle candidate and the basis for SIS

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Date:   Fri, 2 Feb 2018 13:58:46 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Mel Gorman <mgorman@...hsingularity.net>,
        Mike Galbraith <efault@....de>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        LKML <linux-kernel@...r.kernel.org>,
        srinivas.pandruvada@...ux.intel.com
Subject: Re: [PATCH 4/4] sched/fair: Use a recently used CPU as an idle
 candidate and the basis for SIS

On Fri, Feb 02, 2018 at 12:42:29PM +0100, Rafael J. Wysocki wrote:
> > Yes, too many synchronous IPIs, which themselves are typically already
> > more expensive than the MSR access.
> 
> We could do all of the updates in one IPI (as Srinivas said), but it would be
> more code, and custom code for that matter.
> 
> Is this really worth it for a slow path like this one?

Probably not, still, the pattern really annoys me ;-)