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From: Tom W <tcte.tech@gmail.com>
To: Ian Campbell <Ian.Campbell@citrix.com>
Cc: "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: Massive Instant Clock Jump & Freeze domU Issue (NOT Related to Drift, Live Migration or Saving/Restoring)
Date: Tue, 23 Apr 2013 21:26:00 -0400	[thread overview]
Message-ID: <CAHGn6sMxy7QVhtXPefF8Lg0dTRDJDZ=124iaZzGOvMiGspRmkw@mail.gmail.com> (raw)
In-Reply-To: <1366708336.20256.68.camel@zakaz.uk.xensource.com>


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> Does your hypervisor tree have this commit in it:
>
>         commit 84628ee52a427b0f0fe50502eb8ffd0eedad0f03
>         Author: Jan Beulich <jbeulich@suse.com>
>         Date:   Mon Nov 26 17:20:39 2012 +0100
>
>             x86/time: fix scale_delta() inline assembly
>
> That was responsible for a rash of strange time jumps, although IIRC it
> affected the whole system and not individual VMs.
>
> It might be worth looking at the scale_delta function in your kernel,
> which I think you will find in arch/i386/kernel/time-xen.c. There was a
> fix made to this code in the upstream kernel which may be missing there:
>
> http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=de2d1a524e94a79078d9fe22c57c0c6009237547
>
>
After looking at the latest source for RHEL5, the scale_delta method does
not have this change, nor does it have the fix Jan described here:
http://markmail.org/message/cngzubj6b6vdo55a

The latest RHEL6 does however have the change you described above.

Would changing independent_wallclock=1 bypass the need for the domU system
to call this potentially bad scale_delta method in RHEL5?

Thanks Ian.

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  reply	other threads:[~2013-04-24  1:26 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-04-22 22:50 Massive Instant Clock Jump & Freeze domU Issue (NOT Related to Drift, Live Migration or Saving/Restoring) Tom W
2013-04-23  9:12 ` Ian Campbell
2013-04-24  1:26   ` Tom W [this message]
2013-04-24  9:00     ` Ian Campbell
2013-04-23  9:29 ` Jan Beulich
2013-04-23  9:33   ` Ian Campbell
2013-04-23 17:50     ` Tom W

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