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

  • To: Keir Fraser <keir@xxxxxxx>
  • From: Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>
  • Date: Fri, 27 May 2011 15:29:17 +0200
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Fri, 27 May 2011 07:12:21 -0700
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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 Gross                 Principal Developer Operating Systems
TSP ES&S SWE OS6                       Telephone: +49 (0) 89 3222 2967
Fujitsu Technology Solutions              e-mail: juergen.gross@xxxxxxxxxxxxxx
Domagkstr. 28                           Internet: ts.fujitsu.com
D-80807 Muenchen                 Company details: ts.fujitsu.com/imprint.html

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