linux-kernel - Re: acpi throttling: Use this_cpu

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Date:	Mon, 20 Dec 2010 23:28:03 -0500 (EST)
From:	Len Brown <lenb@...nel.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Tejun Heo <htejun@...il.com>, "H. Peter Anvin" <hpa@...or.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	akpm@...ux-foundation.org, Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: acpi throttling: Use this_cpu_has and simplify code

This patch is a valid cleanup, and I've applied it to the acpi-test tree.

The routines named *rdmsr() and *wrmsr() run on the local CPU
by definition.  I think that after this change to get rid of pr*,
that is even more clear.

The part about checking that you are on the right processor
should really be done in the caller.  Yakui should send a patch
for the driver to check for successful return from
set_cpus_allowed_ptr() before invoking this code.

> With the this_cpu_xx we no longer need to pass an acpi
> structure to the msr management code. Simplifies code and improves
> performance.

Simplifies, yes.
Performance -- not the focus here.
If you are running routines to throttle the clock frequency,
then you have already decided that performance isn't your top priority:-)

thanks,
Len Brown, Intel Open Source Technology Center

> Signed-off-by: Christoph Lameter <cl@...ux.com>
> 
> ---
>  drivers/acpi/processor_throttling.c |   32 ++++++++++----------------------
>  1 file changed, 10 insertions(+), 22 deletions(-)

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