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

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Date:	Sun, 05 Aug 2012 10:28:51 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	LEROY christophe <christophe.leroy@....fr>
Cc:	linux-kernel@...r.kernel.org, netdev <netdev@...r.kernel.org>
Subject: Re: Huge performance degradation for UDP between 2.4.17 and 2.6

On Sun, 2012-08-05 at 10:16 +0200, LEROY christophe wrote:
> 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.
> 

I believe you misunderstood me.

I was referring to cpu caches ( dcache & icache )

> 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 ?

I never used SLOB I cannot comment

Please provide (on 3.4.7)

cat /proc/cpuinfo
lsmod
dmesg


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