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Re: RADclock on Xen (was Re: [Xen-devel] [PATCH] time-xen : Reset monoto

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: Re: RADclock on Xen (was Re: [Xen-devel] [PATCH] time-xen : Reset monotonic time when sync up time from dom0 to domU)
From: Darryl Veitch <dveitch@xxxxxxxxxxxxxx>
Date: Thu, 21 Oct 2010 14:36:11 +1100
Cc: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Keir Fraser <keir@xxxxxxx>, Tim Deegan <Tim.Deegan@xxxxxxxxxx>, Shunli Yi <syi@xxxxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>, Saipu Liu <saliu@xxxxxxxxxxxx>, Hang Du <hdu@xxxxxxxxxxxx>, Timothy Broomhead <tim@xxxxxxxxxxxxxxx>, Julien Ridoux <jridoux@xxxxxxxxxxxxxx>
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On 16/10/2010, at 10:21 AM, Jeremy Fitzhardinge wrote:

On 10/15/2010 05:10 AM, Darryl Veitch wrote:
Hi Tim,

good to hear from you.  Dom0 will need the usual RADclock patches
which now integrate the Xen support. These supply two main things:  
i)  kernel level raw timestamping (ie reading of the chosen counter)
of packet arrivals and departures in `good but safe' locations and an
ability to pass those timestamps up (works transparently with pcap,
and doesn't affect its normal operation)

Are you trying to get these changes into mainline Linux?

We are intending to do this, but have not pushed comprehensively yet, though we hope to start soon after we have the adoption into FreeBSD finalised (theoretically around end-2010).  We have had some discussions with John Stultz in preparation.   Would you be interested in being involved in encouraging adoption here ? :-)  

ii)  the ability to access the raw counter of choice from both kernel
and user context

The kernel already has this info, and I have patches for mapping it into
userspace.  Or would a syscall suffice?

We use syscall's currently.


Darryl Veitch
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