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

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Message-ID: <20100129113346.GB1309@gondor.apana.org.au>
Date:	Fri, 29 Jan 2010 22:33:46 +1100
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Krishna Kumar2 <krkumar2@...ibm.com>
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?

On Fri, Jan 29, 2010 at 04:45:01PM +0530, Krishna Kumar2 wrote:
> 
> 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

Hmm, any idea what is causing case 0 to be different from case 2?
In particular, the 64K performance in case 0 appears to be a
regression but in case 2 it's showing up as an improvement.

AFAICS these two cases should produce identical results, or is
this just jitter across tests?

Thanks,
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Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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