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

To: Darryl Veitch <dveitch@xxxxxxxxxxxxxx>
Subject: Re: RADclock on Xen (was Re: [Xen-devel] [PATCH] time-xen : Reset monotonic time when sync up time from dom0 to domU)
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Thu, 21 Oct 2010 13:49:09 -0700
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 10/20/2010 08:36 PM, Darryl Veitch wrote:
> 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 ? :-) 

I'm happy to give you help out where I can.  John is definitely a person
who should be involved.  Where's the current set of patches?

>>> 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.

OK, that's simple.   What do you add?  A new lock time for clock_gettime?


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