From: Jakub Kicinski <kuba@kernel.org>
Date: Thu, 25 Nov 2021 09:44:40 -0800

On Thu, 25 Nov 2021 18:07:08 +0100 Alexander Lobakin wrote:

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This I agree with, and while I can see the layering argument for putting
them into 'ip' and rtnetlink instead of ethtool, I also worry that these
counters will simply be lost in obscurity, so I do wonder if it wouldn't
be better to accept the "layering violation" and keeping them all in the
'ethtool -S' output?  

I don't think we should harm the code and the logics in favor of
'some of the users can face something'. We don't control anything
related to XDP using Ethtool at all, but there is some XDP-related
stuff inside iproute2 code, so for me it's even more intuitive to
have them there.
Jakub, may be you'd like to add something at this point?

TBH I wasn't following this thread too closely since I saw Daniel
nacked it already. I do prefer rtnl xstats, I'd just report them 
in -s if they are non-zero. But doesn't sound like we have an agreement
whether they should exist or not.

Right, just -s is fine, if we drop the per-channel approach.

Can we think of an approach which would make cloudflare and cilium
happy? Feels like we're trying to make the slightly hypothetical 
admin happy while ignoring objections of very real users.

The initial idea was to only uniform the drivers. But in general
you are right, 10 drivers having something doesn't mean it's
something good.

Maciej, I think you were talking about Cilium asking for those stats
in Intel drivers? Could you maybe provide their exact usecases/needs
so I'll orient myself? I certainly remember about XSK Tx packets and
bytes.
And speaking of XSK Tx, we have per-socket stats, isn't that enough?

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+  xdp-channel0-rx_xdp_redirect: 7
+  xdp-channel0-rx_xdp_redirect_errors: 8
+  xdp-channel0-rx_xdp_tx: 9
+  xdp-channel0-rx_xdp_tx_errors: 10
+  xdp-channel0-tx_xdp_xmit_packets: 11
+  xdp-channel0-tx_xdp_xmit_bytes: 12
+  xdp-channel0-tx_xdp_xmit_errors: 13
+  xdp-channel0-tx_xdp_xmit_full: 14

Please leave the per-channel stats out. They make a precedent for
channel stats which should be an attribute of a channel. Working for 
a large XDP user for a couple of years now I can tell you from my own
experience I've not once found them useful. In fact per-queue stats are
a major PITA as they crowd the output.

Oh okay. My very first iterations were without this, but then I
found most of the drivers expose their XDP stats per-channel. Since
I didn't plan to degrade the functionality, they went that way.

Al