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

[Jeremy Fitzhardinge <jeremy@goop.org>]

 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?

    J