Re: [PATCH] fm10k: conditionally disable RSS during device initialization

[Thomas Monjalon <thomas.monjalon@6wind.com>]

Please, anyone to confirm that the patch is valid and must be applied?
This discussion shows some doubts.


2016-03-24 13:35, Michael Frasca:
> Jing,
> 
> Thanks for your assistance. The experiment that you have built should allow you
> to observe the bug. In [5], I would expect that queue 0 receives roughly 1/4 of
> the packets that you sending, assuming the input packets have varied IP
> addresses. Can you measure what % of packets are actually being received in this
> single queue setup (after first running a 4-queue setup)?
> 
> When trying to running with only one RX queue, the fm10k retains the same RSS
> hash function and redirection table that was configured from a previous run. As
> a result, some packets are still being directed to other receive queues. I have
> confirmed this by polling the queue specific stats, which I retrieved via
> rte_eth_xstats_get().
> 
> Looking at fm10k_dev_rss_configure(), one should see that there is no
> modification of fm10k registers when nb_rx_queues == 1. As far as I can tell,
> this is the reason that only a certain partition of packets are being receive in
> a single queue setup (after first running a multi-queue configuration).
> 
> I am unable to access my development environment today, but if you need, I can
> later craft a patch to l3fwd that shows the measurement of packets received at
> each queue.
> 
> Thanks,
> Mike
> 
> 
> > On Mar 24, 2016, at 2:40 AM, Chen, Jing D <jing.d.chen@intel.com> wrote:
> > 
> > Hi, Frasca,
> > 
> > 
> > 
> >> -----Original Message-----
> >> From: Michael Frasca [mailto:michael.frasca@oracle.com <mailto:michael.frasca@oracle.com>]
> >> Sent: Wednesday, March 23, 2016 9:43 PM
> >> To: Chen, Jing D
> >> Cc: dev@dpdk.org <mailto:dev@dpdk.org>
> >> Subject: Re: [PATCH] fm10k: conditionally disable RSS during device
> >> initialization
> >> 
> >> Hi Jing,
> >> 
> >> I ran into this issue while trying to run experiments with different RSS
> >> configurations (no RSS being one cases). It is not clear to me that setting this
> >> register to zero is the best way to disable RSS.
> >> 
> >> After digging further, I have a theory that I'm having this issues because I've
> >> only attached my DPDK application to SR-IOV ports. In
> >> fm10k_dev_dglort_map_configure(), I see that 'RSS Length' is set for the
> >> DGLORT
> >> decoder. However, it appears that this is only invoked for physical functions.
> >> 
> >> Could this be my problem? Is it required that I bind to the physical function
> >> if I want to properly manipulate RSS?
> >> 
> >> Thanks,
> >> Mike
> >> 
> > I don't know exactly what problem you ran into. I think we needn't worry about 
> > those DGLORT setting when using VF device.
> > 
> > I've followed steps to use SRIOV device with RSS enabled and disabled, both
> > are worked well from my side after applying your patch. Below is my setup.
> > 
> > 1. PF with Linux driver "fm10k-next_0.19.3".
> > 2. DPDK with latest code from master branch, apply your patch.
> > 3. Use 1 VF device created by kernel driver.
> > 4. use l3fwd with " ./examples/l3fwd/build/l3fwd -c fc -n 4 -- -p 0x1 --config="(0,0,2),(0,1,2),(0,2,3),(0,3,3)""
> >    with RSS enabled. After sending packets, I can see all 4 queues received packets.
> > 5. use l3fwd with " ./examples/l3fwd/build/l3fwd -c fc -n 4 -- -p 0x1 --config="(0,0,2)""
> >    with RSS disabled. After sending packets, I can see queue 0 received packets.
> > 
> > Can you explain what actual problem is?
> > We can talk offline.
>