linux-kernel - Re: [RFC PATCH 1/9] arm: avoid using on_each

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Date:	Mon, 9 Jan 2012 09:28:15 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Gilad Ben-Yossef <gilad@...yossef.com>
Cc:	linux-kernel@...r.kernel.org,
	Russell King <linux@....linux.org.uk>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	devicetree-discuss@...ts.ozlabs.org,
	Will Deacon <will.deacon@....com>,
	Michal Nazarewicz <mina86@...a86.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Paul Mackerras <paulus@...ba.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Ingo Molnar <mingo@...e.hu>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH 1/9] arm: avoid using on_each_cpu hard coded ret value

On Tue, Jan 03, 2012 at 04:19:05PM +0200, Gilad Ben-Yossef wrote:
> on_each_cpu always returns a hard coded return code of zero.
> 
> Removing all tests based on this return value saves run time
> cycles for compares and code bloat for branches.
> 
> Cc: Michal Nazarewicz <mina86@...a86.com>
> CC: Will Deacon <will.deacon@....com>
> CC: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> CC: Paul Mackerras <paulus@...ba.org>
> CC: Ingo Molnar <mingo@...e.hu>
> CC: Arnaldo Carvalho de Melo <acme@...stprotocols.net>
> CC: Russell King <linux@....linux.org.uk>
> CC: Grant Likely <grant.likely@...retlab.ca>
> CC: Rob Herring <rob.herring@...xeda.com>
> CC: linux-arm-kernel@...ts.infradead.org
> CC: devicetree-discuss@...ts.ozlabs.org
> ---
>  arch/arm/kernel/perf_event.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
> index 88b0941..bfd58d8 100644
> --- a/arch/arm/kernel/perf_event.c
> +++ b/arch/arm/kernel/perf_event.c
> @@ -617,7 +617,7 @@ static int __init
>  cpu_pmu_reset(void)
>  {
>  	if (cpu_pmu && cpu_pmu->reset)
> -		return on_each_cpu(cpu_pmu->reset, NULL, 1);
> +		on_each_cpu(cpu_pmu->reset, NULL, 1);
>  	return 0;
>  }
>  arch_initcall(cpu_pmu_reset);
This patch results in no binary change for my test build with SMP=n and
it saves one instruction on SMP=y.

Acked-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>

Thanks
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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