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Re: [Xen-devel] Re: [PATCH 3/5] x86/pvclock: add vsyscall implementation

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Subject: Re: [Xen-devel] Re: [PATCH 3/5] x86/pvclock: add vsyscall implementation
From: Avi Kivity <avi@xxxxxxxxxx>
Date: Thu, 29 Oct 2009 17:07:26 +0200
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>, kurt.hackel@xxxxxxxxxx, Glauber Costa <glommer@xxxxxxxxxx>, the arch/x86 maintainers <x86@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Glauber de Oliveira Costa <gcosta@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>, zach.brown@xxxxxxxxxx, Ingo Molnar <mingo@xxxxxxxxxx>, chris.mason@xxxxxxxxxx
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On 10/29/2009 04:46 PM, Dan Magenheimer wrote:
No, the apps I'm familiar with (a DB and a JVM) need a timestamp
not a monotonic counter.  The timestamps must be relatively
accurate (e.g. we've been talking about gettimeofday generically,
but these apps would use clock_gettime for nsec resolution),
monotonically increasing, and work properly across a VM
migration.  The timestamps are taken up to a 100K/sec or
more so the apps need to ensure they are using the fastest
mechanism available that meets those requirements.

Out of interest, do you know (and can you relate) why those apps need 100k/sec monotonically increasing timestamps?

--
error compiling committee.c: too many arguments to function


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