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xen-devel
Re: [Xen-devel] [PATCH] Disable Xen PowerNow! support on Opteron 2nd gen
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To: |
Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> |
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Subject: |
Re: [Xen-devel] [PATCH] Disable Xen PowerNow! support on Opteron 2nd gen and earlier processors |
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From: |
"Stephen C. Tweedie" <sct@xxxxxxxxxx> |
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Date: |
Fri, 25 Jan 2008 17:19:53 +0000 |
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Cc: |
Stephen Tweedie <sct@xxxxxxxxxx>, Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Langsdorf, Mark" <mark.langsdorf@xxxxxxx> |
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Fri, 25 Jan 2008 09:21:41 -0800 |
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<C3BD0D29.1B559%Keir.Fraser@xxxxxxxxxxxx> |
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Hi,
On Wed, 2008-01-23 at 15:26 +0000, Keir Fraser wrote:
> > I spent a month trying to debug this and I made no significant
> > progress. If someone who understands Xen timekeeping wants to
> > help me dive into this, I'll be glad to take another stab at
> > it. As it is, even with informing Xen of frequency changes,
> > Xen does not ensure monotinicity.
>
> Seeing them at that frequency (less than one a minute) is not too serious.
> Perhaps we should get rid of the message, or reduce its priority.
They are most definitely serious --- gettimeofday() going backwards
breaks Unix semantics. It breaks applications. It _will_ corrupt
application data --- things like database rollback logs that rely on
timestamp monotonicity to order things correctly will break.
I think this is something that Xen upstream ought to be pretty concerned
about. If we can't fix it properly, then the workaround of disabling
powernow seems to be a must-have.
--Stephen
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- [Xen-devel] [PATCH] Disable Xen PowerNow! support on Opteron 2nd gen and earlier processors, Mark Langsdorf
- RE: [Xen-devel] [PATCH] Disable Xen PowerNow! support on Opteron 2nd gen and earlier processors, Ian Pratt
- RE: [Xen-devel] [PATCH] Disable Xen PowerNow! support on Opteron 2nd gen and earlier processors, Langsdorf, Mark
- RE: [Xen-devel] [PATCH] Disable Xen PowerNow! support on Opteron 2nd gen and earlier processors, Ian Pratt
- RE: [Xen-devel] [PATCH] Disable Xen PowerNow! support on Opteron 2nd gen and earlier processors, Langsdorf, Mark
- Re: [Xen-devel] [PATCH] Disable Xen PowerNow! support on Opteron 2nd gen and earlier processors, Keir Fraser
- Re: [Xen-devel] [PATCH] Disable Xen PowerNow! support on Opteron 2nd gen and earlier processors, Mark Langsdorf
- Re: [Xen-devel] [PATCH] Disable Xen PowerNow! support on Opteron 2nd gen and earlier processors, Keir Fraser
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