Re: [dpdk-dev] DCA

[Bruce Richardson <bruce.richardson@intel.com>]

On Tue, Apr 21, 2015 at 11:51:40AM +0300, Vlad Zolotarov wrote:
> 
> 
> On 04/20/15 13:50, Bruce Richardson wrote:
> >On Mon, Apr 20, 2015 at 01:07:59PM +0300, Vlad Zolotarov wrote:
> >>Hi,
> >>I would like to ask if there is any reason why DPDK doesn't have support for
> >>DCA feature?
> >>
> >>thanks,
> >>vlad
> >With modern platforms with DDIO the data written by the NIC automatically goes
> >into the cache of the CPU without us needing to use DCA.
> Thanks for a reply, Bruce.
> One question though. According to DDIO documentation it only affects the
> CPUs "local" relatively to the NIC. DCA, on the other hand may be configured
> to work with any CPU. Modern platforms usually have a few NUMA nodes and
> requirement of binding network handling threads only to CPUs "local" to the
> NIC is very limiting.
> 
> Could u, pls., comment on this?
> 
> thanks in advance,
> vlad
>
My main comment is that yes, you are correct. DDIO only works with the local
socket, while DCA can be made to work with remote sockets. If you need to do
polling on a device from a remote socket you may need to look at DCA.

Can you perhaps comment on the use-case where you find this binding limiting? Modern
platforms have multiple NUMA nodes, but they also generally have PCI slots
connected to those multiple NUMA nodes also, so that you can have your NIC ports
similarly NUMA partitionned?

/Bruce