[ovs-discuss] ovs-dpdk: can't set n_txq for dpdk interface

[George Diamantopoulos]

Hello again,

To better show the effects of the issue described in my original message,
here's a pastebin link with some information following a clean installation
of debian testing: https://pastebin.com/d8vpvRZr

As you can see, ovs-vsctl does set the n_txq=6 option, but appctl doesn't
register the value in "requested_tx_queues", which seems to be hardcoded to
5 tx queues.
Setting n_txq and n_rxq to low values, such as 2, is not included in the
pastebin above, but as stated in my original message the result is a
failure to bring up to dpdk interfaces (due to rxq=2 being lower than the
hardcoded txq=5, since n_txq is always ignored).

On Sun, 7 Mar 2021 at 05:57, George Diamantopoulos <georgediam at gmail.com>
wrote:

> Hello all,
>
> It appears that setting the n_txq option has no effect for dpdk
> Interfaces, e.g.: "ovs-vsctl set Interface dpdk-eno1 options:n_txq=2".
>
> n_txq appears to be hardcoded to "5" for my driver (BNX2X PMD), for some
> reason.
>
> An additional problem is, the driver won't allow setting n_rxq to a lower
> value than n_txq, and with 5 being hardcoded for txq, it means I can only
> bring the interface up with 5 rxq as well. For 2 ports, that makes 10 PMD
> threads, and I don't want/need to dedicate 10 cores to PMD...
>
> I have tried running DPDK's testpmd with this driver, and it successfully
> starts with 1 rxq + 1 txq, so I believe the issue lies with OVS-DPDK.
>
> Indeed, while there is a call of smap_get_int() in lib/netdev-dpdk.c for
> n_rxq, there doesn't seem to be one for n_txq. I tried a quick hack to fix
> this by replicating dpdk_set_rxq_config() for txq, and calling it
> immediately after dpdk_set_rxq_config() is called in the code (it is called
> only once), but naturally that didn't work. Perhaps
> netdev_dpdk_set_tx_multiq() is involved here, but at that point my
> programming skills are beginning to fail me. Even more frustratingly, I
> can't seem to find where the dreaded number 5 is defined for transmit
> queues in the code...
>
> Are there any known workarounds to this problem? Is it a bug? Thanks!
>
> Best regards,
> George
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.openvswitch.org/pipermail/ovs-discuss/attachments/20210307/53fc5c10/attachment.html>