linux-kernel - Re: [PATCH] sched/idle: Drop !! while calculating 'broadcast'

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Message-ID: <1403612280.29711.115.camel@marge.simpson.net>
Date:	Tue, 24 Jun 2014 14:18:00 +0200
From:	Mike Galbraith <umgwanakikbuti@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Viresh Kumar <viresh.kumar@...aro.org>, mingo@...hat.com,
	linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH] sched/idle: Drop !! while calculating 'broadcast'

On Tue, 2014-06-24 at 10:03 +0200, Peter Zijlstra wrote: 
> On Tue, Jun 24, 2014 at 10:01:01AM +0530, Viresh Kumar wrote:
> > We don't need 'broadcast' to be set to 'zero or one', but to 'zero or non-zero'
> > and so the extra operation to convert it to 'zero or one' can be skipped.
> > 
> > Also change type of 'broadcast' to unsigned int, i.e. type of
> > drv->states[*].flags.
> 
> All true; but does it change anything? That is, does your compiler
> generate better code because of this?

x86_64 gcc-4.8.3 made 1 less instruction, a shift.

-Mike

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