Re: [PATCH net-next] mlx4: Better use of order-0 pages in RX path

On Mon, Mar 13, 2017 at 4:40 PM, Alexei Starovoitov
[off-list ref] wrote:

On Mon, Mar 13, 2017 at 04:28:04PM -0700, Eric Dumazet wrote:

quoted

On Mon, Mar 13, 2017 at 4:21 PM, Alexei Starovoitov
[off-list ref] wrote:

quoted

is it once in the beginning only? If so then why that
'if (!ring->page_cache.index)' check is done for every packet?

You did not really read the patch, otherwise you would not ask these questions.

please explain. I see
+  if (!ring->page_cache.index) {
+          npage = mlx4_alloc_page(priv, ring,
which is done for every packet that goes via XDP_TX.

Well, we do for all packets, even on hosts not running XDP:

if (xdp_prog) { ...

...

Then :

if (doorbell_pending))
     mlx4_en_xmit_doorbell(priv->tx_ring[TX_XDP][cq->ring]);

And nobody complained of few additional instructions.

Should I had, very loudly ?

quoted

Test it, and if you find a regression, shout loudly.

that's not how it works. It's a job of submitter to prove
that additional code doesn't cause regressions especially
when there are legitimate concerns.

I have no easy way to test XDP. I  have never used it and am not
planning to use it any time soon.

Does it mean I no longer can participate to linux dev ?

Nice to hear Alexei.