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

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: RE: [Xen-devel][Pv-ops][PATCH] Netback multiple tasklet support
From: "Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx>
Date: Thu, 10 Dec 2009 11:29:29 +0800
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Thread-topic: [Xen-devel][Pv-ops][PATCH] Netback multiple tasklet support
Jeremy Fitzhardinge wrote:
> On 12/08/09 01:22, Xu, Dongxiao wrote:
>> Jeremy,
>>      I have revised the patch according to your suggestion. See
>> attachment. 0001: Keep group number as 1, and put all the
>> global/static variables to struct xen_netbk. Do some preparations
>> for multiple tasklets support. 0002: Support for netback multiple
>> tasklet. 0003: Use kernel thread to replace the tasklet in order to
>> ensure the dom0 userspace QoS.  
> Thanks, this looks much better.  The only thing which lept out at me
> from a first reading is that "group_nr" is still too generic a name
> for a global symbol.  Something like "xen_netbk_nr_groups" perhaps?

Thanks, I will change the name for it. 

> 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

> 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? 


>      J
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