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

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Message-ID: <3b2646d6-6d52-4479-b082-eb6264e8d6f7@kernel.org>
Date: Wed, 9 Oct 2024 10:35:43 -0600
From: David Ahern <dsahern@...nel.org>
To: Jens Axboe <axboe@...nel.dk>, 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 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 have no doubts this will go much higher per thread, if the link bw was
> there. When I looked at CPU usage for the receiver, the thread itself is
> using ~30% CPU. And then there's some softirq/irq time outside of that,
> but that should ammortize with higher bps rates too I'd expect.
> 
> My nic does have 2 100G ports, so might warrant a bit more testing...
> 

It would be good to see what the next bottleneck is for io_uring with ZC
Rx path. My expectation is that a 200G link is a means to show you (ie.,
you will not hit 200G so cpu monitoring, perf-top, etc will show the
limiter).