Re: RADclock on Xen (was Re: [Xen-devel] [PATCH] time-xen : Reset monotonic time when sync up time from dom0 to domU)

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

 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?

> 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?

> In the Xen context, the choice of counter will end up being Xen
> Clocksource which is already accessible to guests as is already a
> suitable counter of the right size (64-bit).
>
> Take a look at the RADclock downloads
> <http://www.cubinlab.ee.unimelb.edu.au/radclock/download.php> page.
> There have been a number of changes recently in particular in the
> integration of the Xen support so I will direct you to Julien Ridoux
> for finer-grained answers as he and Tim Broomhead actually wrote the
> code. 
>
> We'll be quizzing you shortly about our needs to make this work under
> HV using that way to access the Xenstore you mentioned, and we'd like
> to talk to you about how to improve packet timestamping under Dom0. 

OK.

    J

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