Re: [PATCH] tcp: splice as many packets as possible at once

Willy Tarreau
2009-01-19T00:42:49Z

Hi guys,

On Thu, Jan 15, 2009 at 03:54:34PM -0800, David Miller wrote:
> From: Willy Tarreau <w@1wt.eu>
> Date: Fri, 16 Jan 2009 00:44:08 +0100
>
> > And BTW feel free to add my Tested-by if you want in case you merge
> > this fix.
>
> Done, thanks Willy.

Just for the record, I've now re-integrated those changes in a test kernel
that I booted on my 10gig machines. I have updated my user-space code in
haproxy to run a new series of tests. Eventhough there is a memcpy(), the
results are EXCELLENT (on a C2D 2.66 GHz using Myricom's Myri10GE NICs) :

- 4.8 Gbps at 100% CPU using MTU=1500 without LRO
(3.2 Gbps at 100% CPU without splice)

- 9.2 Gbps at 50% CPU using MTU=1500 with LRO

- 10 Gbps at 20% CPU using MTU=9000 without LRO (7 Gbps at 100% CPU without
splice)

- 10 Gbps at 15% CPU using MTU=9000 with LRO

These last ones are really impressive. While I had already observed such
performance on the Myri10GE with Tux, it's the first time I can reach that
level with so little CPU usage in haproxy !

So I think that the memcpy() workaround might be a non-issue for some time.
I agree it's not beautiful but it works pretty well for now.

The 3 patches I used on top of 2.6.27.10 were the fix to return 0 intead of
-EAGAIN on end of read, the one to process multiple skbs at once, and Dave's
last patch based on Jarek's workaround for the corruption issue.

Cheers,
Willy