RE: [PATCH] examples/multi_process: add options to control port configuration

["Ma, WenwuX" <wenwux.ma@intel.com>]

> -----Original Message-----
> From: Richardson, Bruce <bruce.richardson@intel.com>
> Sent: 2022年2月18日 17:42
> To: Ma, WenwuX <wenwux.ma@intel.com>
> Cc: Burakov, Anatoly <anatoly.burakov@intel.com>; dev@dpdk.org; Hu,
> Jiayu <jiayu.hu@intel.com>; Wang, Yinan <yinan.wang@intel.com>; He,
> Xingguang <xingguang.he@intel.com>
> Subject: Re: [PATCH] examples/multi_process: add options to control port
> configuration
> 
> On Fri, Feb 18, 2022 at 06:49:19AM +0000, Ma, WenwuX wrote:
> >
> >
> > > -----Original Message-----
> > > From: Richardson, Bruce <bruce.richardson@intel.com>
> > > Sent: 2022年2月17日 17:06
> > > To: Ma, WenwuX <wenwux.ma@intel.com>
> > > Cc: Burakov, Anatoly <anatoly.burakov@intel.com>; dev@dpdk.org; Hu,
> > > Jiayu <jiayu.hu@intel.com>; Wang, Yinan <yinan.wang@intel.com>; He,
> > > Xingguang <xingguang.he@intel.com>
> > > Subject: Re: [PATCH] examples/multi_process: add options to control
> > > port configuration
> > >
> > > On Thu, Feb 17, 2022 at 03:17:55PM +0000, Wenwu Ma wrote:
> > > > The default values of rx mq_mode and rx offloads for port will
> > > > cause symmetric_mp startup failure if the port do not support rss or
> csum.
> > > > Therefore, we added two new options --rx-mq-mode and
> > > > --rx-offloads, through which the user can set the values
> > > > appropriately according to the situation to make app startup normally.
> > > >
> > > > Signed-off-by: Wenwu Ma <wenwux.ma@intel.com> ---
> > >
> > > The idea seems reasonable enough, but I think the implementation
> > > requiring the user to pass in special "magic numbers" for the
> > > offload values is not a good idea. Perhaps add in a separate flag for "no-
> csum" to disable that.
> > >
> > > For the no-rss case, can you explain how you would see this app
> > > being used in the absense of RSS support to distribute traffic among
> > > the separate processes?
> >
> > When app run in qemu vm and the backend is dpdk vhost, it will report
> error below:
> > "virtio_dev_configure(): RSS support requested but not supported by the
> device"
> 
> Sure, I understand that. But how does it make sense to run multiple copies of
> the app if RSS cannot be used to spread the traffic between the instances?

in test case, vhost backend has 2 queues, and we set fwd as txonly, and in vm, we run app as follows

./examples/multi_process/symmetric_mp/build/symmetric_mp -l 1 -n 4 --proc-type=auto -- -p 3 --num-procs=2 --proc-id=0
./examples/multi_process/symmetric_mp/build/symmetric_mp -l 2 -n 4 --proc-type=secondary -- -p 3 --num-procs=2 --proc-id=1

So,  instance 0 receive pkts in queue 0, and instance 1 receive pkts in queue 1.