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

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

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

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