[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH] Deferrable Timer




Yu, Ke wrote:

Yu, Ke wrote:
Dave,

Glad to see there is deferrable timer application. Please go ahead
with that. And I will keep you updated if there is finding in my side.

BTW, Could you please elaborate more on the
"guest-handles-missed-tick" case? Since there is no need to inject
missed tick to guest, which timer would be used as deferrable timer?

Oh, I catch your points now, please ignore my previous question. You
actually means that: since guest can handle the missed tick correcty, it
is acceptable that the hpet/vpt timer is defered, so the hpet/vpt timer
itself can be deferrable timer.

Yes.

so is the
"guest-does-not-handle-missed-ticks" case, since xen can handle that by
inject missed tick respectively.
For the guest-does-not-handle-missed-ticks case we inject the correct number
of interrupts, i.e. N*period, N an integer, but we can delay a bit before
doing so. So I think we can use deferrable timers for both policies.

If my understanding is correct, I would say your point is truly good, I
expect this will reduce the timer count much especially when there is
multiple HVMs.
Best Regards
Ke

Best Regards
Ke

Dave Winchell wrote:
Ke,

One would think that hpet or vpt support for the
guest-handles-missed-ticks policy would be a good application for a
deferrable timer. If a deferrable timer were used, then the
comparator (cmp) would have to be warped to a non-integer multiple
of the period. This is because Linux reads the comparator register
to estimate the delay since the interrupt was posted.
I don't think warping like this will be a problem. At some point, I
can test this.
I think we could use the deferrable timer for the
guest-does-not-handle-missed-ticks
policy as well.

Any investigation that you want to do in the platform timer area
would be fine. Or I can do it, but that will probably be after I do
the vpt.c/hpet.c integration work.

thanks,
Dave

Best Regards
Ke

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel


 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.