Re: [dpdk-dev] [PATCH v2] net/af_packet: fix ignoring full ring on tx

[Tudor Cornea <tudor.cornea@gmail.com>]

On Tue, 26 Oct 2021 at 17:41, Ferruh Yigit <ferruh.yigit@intel.com> wrote:

> Hi Tudor,
>
> I have used testpmd, 'txonly' forwarding. Tx recovers after interface up,
> but by adding some debug logs I can see 'poll()' returns with POLLOUT even
> there is no space in the buffer.
>
> According the logic in the PMD, when 'poll()' returns success, it expects
> to have some space in the Tx buffer.
>
> So I agree to add the check.
>
> Only have a question on the POLLERR, should we separate the POLLERR check
> to cover ifdown case, what do you think about following logic:
>
> if (!TP_STATUS_AVAILABLE) {
>      if (poll() < 0)
>          break;
>      if (pfd.revents & POLLERR)
>          break;
> }
>
> if (!TP_STATUS_AVAILABLE)
>      break;
>
>
Hi Ferruh,

Thanks for the suggestion.
I was thinking of adding this check, and intuitively, it seems correct. I
tried to do some further testing.

I tested with the POLLERR check, and I don't see the issue anymore.
However, if I remove the second if (!TP_STATUS_AVAILABLE), I seem to get
bursts of 2048 packets followed by periods of not sending anything when
toggling the interface link state.
Without the second if(!TP_STATUS_AVAILABLE) statement, the issue seems to
reproduce, regardless if I add the check for POLLERR or not.

RxB=0 RxP=0 TxB=0 TxP=0
RxB=0 RxP=0 TxB=0 TxP=0
RxB=0 RxP=0 TxB=0 TxP=0
RxB=0 RxP=0 TxB=0 TxP=0
RxB=0 RxP=0 TxB=0 TxP=0
RxB=0 RxP=0 TxB=0 TxP=0
RxB=0 RxP=0 TxB=0 TxP=0
RxB=0 RxP=0 TxB=606208 TxP=2048
RxB=0 RxP=0 TxB=0 TxP=0
RxB=0 RxP=0 TxB=0 TxP=0

I will send an updated version of the patch.

Thanks,
Tudor