linux-kernel - Re: [Use cpuops V1 02/11] vmstat: Optimize zone counter modifications through the use of this cpu operations

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Message-ID: <4CFE3DF8.8080405@kernel.org>
Date:	Tue, 07 Dec 2010 15:00:24 +0100
From:	Tejun Heo <tj@...nel.org>
To:	Christoph Lameter <cl@...ux.com>
CC:	akpm@...ux-foundation.org, Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [Use cpuops V1 02/11] vmstat: Optimize zone counter modifications
 through the use of this cpu operations

On 12/06/2010 06:16 PM, Christoph Lameter wrote:
> this cpu operations can be used to slightly optimize the function. The
> changes will avoid some address calculations and replace them with the
> use of the percpu segment register.
> 
> If one would have this_cpu_inc_return and this_cpu_dec_return then it
> would be possible to optimize inc_zone_page_state and dec_zone_page_state even
> more.
> 
> V1->V2:
> 	- Fix __dec_zone_state overflow handling
> 	- Use s8 variables for temporary storage.
> 
> V2->V3:
> 	- Put __percpu annotations in correct places.
> 
> Reviewed-by: Pekka Enberg <penberg@...nel.org>
> Signed-off-by: Christoph Lameter <cl@...ux.com>

> @@ -221,16 +223,19 @@ EXPORT_SYMBOL(mod_zone_page_state);
...
> +		__this_cpu_write(*p, - overstep);

Applied to percpu#for-next with the space after '-' removed from the
above line.

Thanks.

-- 
tejun
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