Re: [Xen-devel] [PATCH] use per-cpu variables in cpufreq

To:	Keir Fraser <keir@xxxxxxx>
Subject:	Re: [Xen-devel] [PATCH] use per-cpu variables in cpufreq
From:	Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>
Date:	Fri, 27 May 2011 15:29:17 +0200
Cc:	xen-devel@xxxxxxxxxxxxxxxxxxx
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On 05/27/11 15:11, Keir Fraser wrote:

On 27/05/2011 12:11, "Juergen Gross"<juergen.gross@xxxxxxxxxxxxxx>  wrote:

The cpufreq driver used some local arrays indexed by cpu number. This patch
replaces those arrays by per-cpu variables. The AMD and INTEL specific parts
used different per-cpu data structures with nearly identical semantics.
Fold the two structures into one by adding a generic architecture data item.

Xen's per-cpu data gets freed across cpu offline/online, whereas cpu-indexed
arrays of course do not. Will the cpufreq state be correctly handled across
offline/online if we switch to per-cpu vars?


As far as I could see, yes. The data should only be used for cpus with
a valid acpid->cpuid translation, which is created when a cpu is going
online and destroyed when it is going offline again.
It would be nice, however, if the INTEL and/or AMD code owners could
give an ack on this...


Juergen

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Juergen Gross                 Principal Developer Operating Systems
TSP ES&S SWE OS6                       Telephone: +49 (0) 89 3222 2967
Fujitsu Technology Solutions              e-mail: juergen.gross@xxxxxxxxxxxxxx
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Re: [Xen-devel] [PATCH] use per-cpu variables in cpufreq