Re: [Xen-devel] million cycle interrupt

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 14/04/2009 05:23, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

>> If it's really caused by SMT, it's more likely to be software
>> caused resource contention due to doubled logical processors.
> 
> You mentioned PIT earlier... I wonder if PIT can be
> read in parallel if read from different cores, but
> if read from different threads, it must be serialized?
> A million cycles is probably about right for a platform
> timer read, true?

You could validate that quite easily by adding your own timer read wrapped
in TSC reads. Actually a PIT read, even though it requires multiple accesses
over the ISA bus, should take less than 10us.

 -- Keir



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