netdev - Re: 10GBE performance drop with net.ipv4.tcp

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Date:	Wed, 20 Jun 2012 09:00:50 +0200
From:	Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: 10GBE performance drop with net.ipv4.tcp_timestamps=0

Am 19.06.2012 23:31, schrieb Eric Dumazet:
> On Tue, 2012-06-19 at 23:08 +0200, Stefan Priebe wrote:
>> i'm testing 10GBE speed with tweo servers. One with 3.5-rc3 nd thoe
>> other one whith RHEL 6 (2.6.32 kernel).
>>
>> I noticed that setting
>> net.ipv4.tcp_timestamps=0
>>
>> descreased the performance from 9,7 Full Duplex to 3-4Gb/s.
>>
>> Is this bahviour fine? What should / could i tet?
>>
>
> Really, you should provide more input than that, if you really want us
> to help.

*arg* forgot to add the pastebin links. Sorry. Speed degraded in this 
case from 9,88Gbit/s to 2,45Gbit/s. When i turn on timestamps it's 
perfect again. Server A has 3.5.0-rc3 and server B has an RHEL6 2.6.32 
kernel.

Before:
http://pastebin.com/raw.php?i=1gVraWVc

After:
http://pastebin.com/raw.php?i=NSh8Y29s

Thanks,
Stefan

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