linux-kernel - Re: [PATCH] sched: Fast idling of CPU when system is partially loaded

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Message-ID: <20140617120938.GN3213@twins.programming.kicks-ass.net>
Date:	Tue, 17 Jun 2014 14:09:38 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Tim Chen <tim.c.chen@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Andi Kleen <andi@...stfloor.org>,
	Michel Lespinasse <walken@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Peter Hurley <peter@...leysoftware.com>,
	Jason Low <jason.low2@...com>,
	Davidlohr Bueson <davidlohr@...com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: Fast idling of CPU when system is partially loaded

On Mon, Jun 16, 2014 at 08:50:07AM -0700, Tim Chen wrote:
> > The worry I have is that this update is 'slow'. We could have grown many
> > tasks since the last update.
> 
> The update to turn on the indicator is immediate and triggered in
> add_nr_running. So if there are more than one tasks on any cpu, 
> we start load balancing again right away.  It is only the 
> clearing of the indicator in update_sd_lb_stats that takes time.
> That does no harm as the cleared indicator is for the skipping of load
> balance, which can be delayed.
> 

Oh right, shows me I shouldn't be reading patches on sunday or similarly
daft times ;)

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