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Re: [Xen-devel] performance counters
| To: | Jan Beulich <jbeulich@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] performance counters |
| From: | Keir Fraser <keir@xxxxxxxxxxxxx> |
| Date: | Thu, 15 Mar 2007 11:58:58 +0000 |
| Delivery-date: | Thu, 15 Mar 2007 04:58:16 -0700 |
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| Thread-topic: | [Xen-devel] performance counters |
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On 15/3/07 11:27, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote: > In order to be meaningful and usable together with other measuring methods, > their use in my opinion should impose as little overhead as possible. With > that, > I wonder why per-cpu counters use atomic operations. Well, they shouldn't be. Nearly all (apart from the array/histogram ones) are per-cpu anyway. And even if they weren't, a few lost increments wouldn't matter (assuming the read and write parts of the increment are each themselves atomic -- otherwise you could get worse write-conflict problems like word tearing). -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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