Re: [dpdk-dev] [PATCH 2/4] net/mlx5: add support for Rx queue delay drop

[David Marchand <david.marchand@redhat.com>]

On Thu, Nov 4, 2021 at 12:27 PM Bing Zhao <bingz@nvidia.com> wrote:
>
> For an Ethernet RQ, packets received when receive WQEs are exhausted
> are dropped. This behavior prevents slow or malicious software
> entities at the host from affecting the network. While for hairpin
> cases, even if there is no software involved during the packet
> forwarding from Rx to Tx side, some hiccup in the hardware or back
> pressure from Tx side may still cause the WQEs to be exhausted. In
> certain scenarios it may be preferred to configure the device to
> avoid such packet drops, assuming the posting of WQEs will resume
> shortly.
>
> To support this, a new devarg "delay_drop_en" is introduced, by
> default, the delay drop is enabled for hairpin Rx queues and
> disabled for standard Rx queues. This value is used as a bit mask:
>   - bit 0: enablement of standard Rx queue
>   - bit 1: enablement of hairpin Rx queue
> And this attribute will be applied to all Rx queues of a device.

Rather than a devargs, why can't the driver use this option in the
identified usecases where it makes sense?
Here, hairpin.


-- 
David Marchand