netdev - Re: [PATCH v1 00/15] io

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Message-ID: <b8fd4a5b-a7eb-45a7-a2f4-fce3b149bd5b@kernel.dk>
Date: Wed, 9 Oct 2024 11:12:56 -0600
From: Jens Axboe <axboe@...nel.dk>
To: David Ahern <dsahern@...nel.org>, David Wei <dw@...idwei.uk>,
 io-uring@...r.kernel.org, netdev@...r.kernel.org
Cc: Pavel Begunkov <asml.silence@...il.com>, Jakub Kicinski
 <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jesper Dangaard Brouer <hawk@...nel.org>,
 Mina Almasry <almasrymina@...gle.com>
Subject: Re: [PATCH v1 00/15] io_uring zero copy rx

On 10/9/24 10:53 AM, Jens Axboe wrote:
> On 10/9/24 10:50 AM, Jens Axboe wrote:
>> On 10/9/24 10:35 AM, David Ahern wrote:
>>> On 10/9/24 9:43 AM, Jens Axboe wrote:
>>>> Yep basically line rate, I get 97-98Gbps. I originally used a slower box
>>>> as the sender, but then you're capped on the non-zc sender being too
>>>> slow. The intel box does better, but it's still basically maxing out the
>>>> sender at this point. So yeah, with a faster (or more efficient sender),
>>>
>>> I am surprised by this comment. You should not see a Tx limited test
>>> (including CPU bound sender). Tx with ZC has been the easy option for a
>>> while now.
>>
>> I just set this up to test yesterday and just used default! I'm sure
>> there is a zc option, just not the default and hence it wasn't used.
>> I'll give it a spin, will be useful for 200G testing.
> 
> I think we're talking past each other. Yes send with zerocopy is
> available for a while now, both with io_uring and just sendmsg(), but
> I'm using kperf for testing and it does not look like it supports it.
> Might have to add it... We'll see how far I can get without it.

Stanislav pointed me at:

https://github.com/facebookexperimental/kperf/pull/2

which adds zc send. I ran a quick test, and it does reduce cpu
utilization on the sender from 100% to 95%. I'll keep poking...

-- 
Jens Axboe