netdev - Re: consistency for statistics with XDP mode

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Message-Id: <20181203.160045.348991720664159909.davem@davemloft.net>
Date:   Mon, 03 Dec 2018 16:00:45 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     toke@...e.dk
Cc:     dsahern@...il.com, brouer@...hat.com, saeedm@...lanox.com,
        mst@...hat.com, netdev@...r.kernel.org, pstaszewski@...are.pl,
        jasowang@...hat.com
Subject: Re: consistency for statistics with XDP mode

From: Toke Høiland-Jørgensen <toke@...e.dk>
Date: Mon, 03 Dec 2018 22:00:32 +0200

> I wonder if it would be possible to support both the "give me user
> normal stats" case and the "let me do whatever I want" case by a
> combination of userspace tooling and maybe a helper or two?
> 
> I.e., create a "do_stats()" helper (please pick a better name), which
> will either just increment the desired counters, or set a flag so the
> driver can do it at napi poll exit. With this, the userspace tooling
> could have a "--give-me-normal-stats" switch (or some other interface),
> which would inject a call instruction to that helper at the start of the
> program.
> 
> This would enable the normal counters in a relatively painless way,
> while still letting people opt out if they don't want to pay the cost in
> terms of overhead. And having the userspace tooling inject the helper
> call helps support the case where the admin didn't write the XDP
> programs being loaded.
> 
> Any reason why that wouldn't work?

I think this is a good idea, or even an attribute tag that gets added
to the XDP program that controls stats handling.