Re: [Pv-ops][PATCH] Netback multiple tasklet support

[Jeremy Fitzhardinge <jeremy@goop.org>]

On 12/09/09 19:29, Xu, Dongxiao wrote:
>> Also, is it worth making it a tunable?  Presumably it needn't scale
>> exactly with the number of dom0 cpus; if you only have one or two gbit
>> interfaces, then you could saturate that pretty quickly with a small
>> number of cpus, regardless of how many domains you have.
>>      
> How many CPUs are serving for the NIC interface is determined by how
> interrupt is delivered. If system only has two gbit interfaces, and they
> delivier interrupts to CPU0 and CPU1, then the case is: two CPUs handle
> two tasklets. Other CPUs are idle. The group_nr just defines the max
> number of tasklets, however it doesn't decide how tasklet is handled by
> CPU.
>    

So does this mean that a given vcpu will be used to handle the interrupt 
if happens to be running on a pcpu with affinity for the device?  Or 
that particular devices will be handled by particular vcpus?

>> I've pushed this out in its own branch:
>> xen/dom0/backend/netback-tasklet; please post any future patches
>> against this branch.
>>      
> What's my next step for this netback-tasklet tree merging into xen/master?
>    

Hm, well, I guess:

    * I'd like to see some comments Keir/Ian(s)/others that this is
      basically the right approach.  It looks OK to me, but I don't have
      much experience with performance in the field.
          o does nc2 make nc1 obsolete?
    * Testing to make sure it really works.  Netback is clearly critical
      functionality, so I'd like to be sure we're not introducing big
      regressions

     J