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Re: [Xen-devel] [PATCH] per-cpu timer changes
| To: | Don Fry <brazilnut@xxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] [PATCH] per-cpu timer changes |
| From: | Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> |
| Date: | Thu, 26 May 2005 19:01:09 +0100 |
| Cc: | Xen-devel@xxxxxxxxxxxxxxxxxxx |
| Delivery-date: | Thu, 26 May 2005 17:56:48 +0000 |
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| In-reply-to: | <20050526173457.GA4725@xxxxxxxxxx> |
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On 26 May 2005, at 18:34, Don Fry wrote: The time going backwards was only occasionally, and it was a BIG jump backwards. I tracked it down yesterday to a problem with doing 32-bit arithmetic in Linux on the tsc values. For some reason, every 5-20 minutes xen seems to pause for about 5 seconds. This causes the tsc to wrap if only 32-bits are used, and the 'time went backwards' message isprinted. I changed to use 64-bit tsc deltas and have been running sinceyesterday afternoon without any 'time went backwards' messages. I want to do some more cleanup (remove my debugging code) and will post all my changes to the list this afternoon. It would be good to know where those 5 seconds go. Doing 64-bit arithmetic on x86 will be slower and possibly fudge over the underlying problem. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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