linux-kernel - Re: Huge performance degradation for UDP between 2.4.17 and 2.6

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Date:	Sun, 05 Aug 2012 10:16:05 +0200
From:	LEROY christophe <christophe.leroy@....fr>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: Huge performance degradation for UDP between 2.4.17 and 2.6

Le 02/08/2012 16:13, Eric Dumazet a écrit :
> On Thu, 2012-08-02 at 14:27 +0200, leroy christophe wrote:
>> Hi
>>
>> I'm having a big issue with UDP. Using a powerpc board (MPC860).
>>
>> With our board running kernel 2.4.17, I'm able to send 160000 voice
>> packets (UDP, 96 bytes per packet) in 11 seconds.
>> With the same board running either Kernel 2.6.35.14 or Kernel 3.4.7, I
>> need 55 seconds to send the same amount of packets.
>>
>>
>> Is there anything to tune in order to get same output rate as with
>> Kernel 2.4 ?
> kernel size is probably too big for your old / slow cpu.
>
> Maybe you added too many features on your 3.4.7 kernel. (netfilter ?
> SLUB debugging ...)
>
> Its hard to say, 2.4.17 had less features and was faster.
>

Thanks for your answer.
Yes I have netfilter as I need it. However, I tried without it and still 
need about 37 seconds to send the 160000 packets I was sending in 11 
seconds with 2.4.17

I don't think there is any problem with size of the kernel. I still have 
plenty of memory available.

All debugging is turned off, and I'm not using SLUB but SLOB.
I have 32Mbytes of RAM. Would SLUB be more performant than SLOB ?

Christophe
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