linux-kernel - Re: [PATCH net-next 00/10] net: faster and simpler CRC32C computation

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Message-ID: <CAMj1kXFSm9-5+uBoF3mBbZKRU6wK9jmmyh=L538FoGvZ1XVShQ@mail.gmail.com>
Date: Sun, 11 May 2025 23:45:14 +0200
From: Ard Biesheuvel <ardb@...nel.org>
To: Andrew Lunn <andrew@...n.ch>
Cc: Eric Biggers <ebiggers@...nel.org>, netdev@...r.kernel.org, 
	linux-nvme@...ts.infradead.org, linux-sctp@...r.kernel.org, 
	linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Daniel Borkmann <daniel@...earbox.net>, Marcelo Ricardo Leitner <marcelo.leitner@...il.com>, 
	Sagi Grimberg <sagi@...mberg.me>
Subject: Re: [PATCH net-next 00/10] net: faster and simpler CRC32C computation

On Sun, 11 May 2025 at 23:22, Andrew Lunn <andrew@...n.ch> wrote:
>
> On Sun, May 11, 2025 at 10:29:29AM -0700, Eric Biggers wrote:
> > On Sun, May 11, 2025 at 06:30:25PM +0200, Andrew Lunn wrote:
> > > On Sat, May 10, 2025 at 05:41:00PM -0700, Eric Biggers wrote:
> > > > Update networking code that computes the CRC32C of packets to just call
> > > > crc32c() without unnecessary abstraction layers.  The result is faster
> > > > and simpler code.
> > >
> > > Hi Eric
> > >
> > > Do you have some benchmarks for these changes?
> > >
> > >     Andrew
> >
> > Do you want benchmarks that show that removing the indirect calls makes things
> > faster?  I think that should be fairly self-evident by now after dealing with
> > retpoline for years, but I can provide more details if you need them.
>
> I was think more like iperf before/after? Show the CPU load has gone
> down without the bandwidth also going down.
>
> Eric Dumazet has a T-Shirt with a commit message on the back which
> increased network performance by X%. At the moment, there is nothing
> T-Shirt quotable here.
>

I think that removing layers of redundant code to ultimately call the
same core CRC-32 implementation is a rather obvious win, especially
when indirect calls are involved. The diffstat speaks for itself, so
maybe you can print that on a T-shirt.