netdev - Re: [PATCH net-next v3 00/10] UDP/IPv6 refactoring

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Message-ID: <212de77f-6ad1-e012-9b49-8b5cebaded63@gmail.com>
Date:   Mon, 16 May 2022 21:48:58 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 00/10] UDP/IPv6 refactoring

On 5/16/22 14:48, Paolo Abeni wrote:
> Hello,
> 
> On Fri, 2022-05-13 at 16:26 +0100, Pavel Begunkov wrote:
>> Refactor UDP/IPv6 and especially udpv6_sendmsg() paths. The end result looks
>> cleaner than it was before and the series also removes a bunch of instructions
>> and other overhead from the hot path positively affecting performance.
>>
>> Testing over dummy netdev with 16 byte packets yields 2240481 tx/s,
>> comparing to 2203417 tx/s previously, which is around +1.6%
> 
> I personally feel that some patches in this series have a relevant
> chance of introducing functional regressions and e.g. syzbot will not
> help to catch them. That risk is IMHO relevant considered that the
> performance gain here looks quite limited.

I can't say I agree with that. First, I do think the code is much
cleaner having just one block checking corking instead of a couple
of random ifs in different places. Same for sin6. Not to mention
negative line count.

Also, assuming this 1.6% translates to ~0.5-1% with fast NICs, that's
still huge, especially when we get >5GB/s in single core zc tests b/w
servers.

If maintainers are not merging it, I think I'll delay the series until
I get another batch of planned optimisations implemented on top.


> There are a few individual changes that IMHO looks like nice cleanup
> e.g. patch 5, 6, 8, 9 and possibly even patch 1.
> 
> I suggest to reduce the patchset scope to them.

-- 
Pavel Begunkov