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Re: [Xen-devel] [PATCH] Avoid endless loop for vcpu migration
| To: | Keir Fraser <keir.xen@xxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] [PATCH] Avoid endless loop for vcpu migration |
| From: | Juergen Gross <juergen.gross@xxxxxxxxxxxxxx> |
| Date: | Tue, 15 Mar 2011 09:53:02 +0100 |
| Cc: | xen-devel@xxxxxxxxxxxxxxxxxxx, Jan Beulich <JBeulich@xxxxxxxxxx> |
| Delivery-date: | Tue, 15 Mar 2011 01:53:39 -0700 |
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On 03/15/11 09:50, Keir Fraser wrote: On 15/03/2011 08:46, "Juergen Gross"<juergen.gross@xxxxxxxxxxxxxx> wrote:It's not critical, and not affecting correctness. But with updating idle_bias on the first invocation you're (on the right hardware) basically guaranteeing the second invocation to return a different CPU. That way, your loop will be run minimally three times on such systems. I already find it odd to require two iterations when previously this was a strait code path.This was wrong. It was always required to hold the schedule lock of the picked cpu as well, otherwise a race with cpu hotplug would be possible.What would that race be? CPU offlining is done in stop_machine context. Ahh, okay. Juergen -- 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 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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