netdev - Re: [RFC] [PATCH] Optimize TCP sendmsg in favour of fast devices?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <OFA813CB35.7FC6144E-ON652576BA.003C3B2C-652576BA.003CB215@in.ibm.com>
Date:	Fri, 29 Jan 2010 16:45:01 +0530
From:	Krishna Kumar2 <krkumar2@...ibm.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	David Miller <davem@...emloft.net>, eric.dumazet@...il.com,
	ilpo.jarvinen@...sinki.fi, netdev@...r.kernel.org
Subject: Re: [RFC] [PATCH] Optimize TCP sendmsg in favour of fast devices?

> Herbert Xu <herbert@...dor.apana.org.au> wrote on 01/29/2010 02:36:25 PM:
>
> > I ran 5 serial netperf's with 16K and another 5 serial netperfs
> > with 64K I/O sizes, and the aggregate result is:
> >
> > 0. Driver unsets F_SG but sets F_GSO:
> >       Original code with 16K: 19471.65
> >       New code with 16K:      19409.70
> >       Original code with 64K: 21357.23
> >       New code with 64K:      22050.42
>
> OK this is more in line with what I was expecting, namely that
> enabling GSO is actually beneficial even without SG.
>
> It would be good to get the CPU utilisation figures so we can
> see the complete picture.

Same 5 runs of single netperf's:

0. Driver unsets F_SG but sets F_GSO:
        Org (16K):      BW: 18180.71    SD: 13.485
        New (16K):      BW: 18113.15    SD: 13.551
        Org (64K):      BW: 21980.28    SD: 10.306
        New (64K):      BW: 21386.59    SD: 10.447

1. Driver unsets F_SG, and with GSO off
        Org (16K):      BW: 10894.62    SD: 26.591
        New (16K):      BW: 7262.10     SD: 35.340
        Org (64K):      BW: 12396.41    SD: 23.357
        New (64K):      BW: 7853.02     SD: 32.405


2. Driver unsets F_SG and uses ethtool to set GSO:
        Org (16K):      BW: 18094.11    SD: 13.603
        New (16K):      BW: 17952.38    SD: 13.743
        Org (64K):      BW: 21540.78    SD: 10.771
        New (64K):      BW: 21818.35    SD: 10.598

> > I should have mentioned this too - if I unset F_SG in the
> > cxgb3 driver and nothing else, ethtool -k still shows GSO
> > is set, and tcpdump shows max packet size is 1448. If I
> > additionally set GSO in driver, then ethtool still has the
> > same output, but tcpdump shows max packet size of 65160.
>
> This sounds like a bug.

Yes, an ethtool bug (version 6). The test case #1 above, I
have written that GSO is off but ethtool "thinks" it is on
(after a modprobe -r cxgb3; modprobe cxgb3). So for test #2,
I simply run "ethtool ... gso on", and GSO is now really on
in the kernel, explaining the better results.

thanks,

- KK

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html