linux-kernel - Re: [PATCH 2/5] powernow-k8: Add core performance boost support

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Date:	Tue, 23 Mar 2010 17:26:40 +0100
From:	Borislav Petkov <bp@...64.org>
To:	Dominik Brodowski <linux@...inikbrodowski.net>
Cc:	Thomas Renninger <trenn@...e.de>, akpm@...ux-foundation.org,
	davej@...hat.com, cpufreq@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 2/5] powernow-k8: Add core performance boost support

From: Dominik Brodowski <linux@...inikbrodowski.net>
Date: Tue, Mar 23, 2010 at 03:47:57PM +0100

> > > If it's a percpu var, isn't it local anyway?
> > 
> > I meant driver-local. So that I don't have to deref even the per_cpu var
> > and thus save some cycles.
> 
> Well, it doesn't seem to be used in any hot path (and if it were, using a
> per-cpu var was better anyway, because of no contention etc.). If it really
> saves some cycles, I'm more than fine with keeping it; still, informing the
> user in /proc/cpuinfo seems like a sensible thing to do.

No, the idea was to do the local caching _in addition_ to advertising it
over /proc/cpuinfo. Let's see what the x86 maintainers think though...

-- 
Regards/Gruss,
Boris.

--
Advanced Micro Devices, Inc.
Operating Systems Research Center
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