netdev - Re: e1000: Question about polling

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Date:	Wed, 20 Feb 2008 07:50:54 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Badalian Vyacheslav <slavon@...telecom.ru>
Cc:	netdev@...r.kernel.org
Subject: Re: e1000: Question about polling

On 18-02-2008 10:18, Badalian Vyacheslav wrote:
> Hello all.

Hi,

> Interesting think:
> 
> Have PC that do NAT. Bandwidth about 600 mbs.
> 
> Have  4 CPU (2xCoRe 2 DUO "HT OFF" 3.2 HZ).
> 
> irqbalance in kernel is off.
> 
> nat2 ~ # cat /proc/irq/217/smp_affinity
> 00000001
> nat2 ~ # cat /proc/irq/218/smp_affinity
> 00000003
> 
> Load SI on CPU0 and CPU1 is about 90%
> 
> Good... try do
> echo ffffffff > /proc/irq/217/smp_affinity
> echo ffffffff > /proc/irq/218/smp_affinity
> 
> Get 100% SI at CPU0
> 
> Question Why?

I think you should show here /proc/interrupts in all these cases.

> 
> I listen that if use IRQ from 1 netdevice to 1 CPU i can get 30% 
> perfomance... but i have 4 CPU... i must get more perfomance if i cat 
> "ffffffff"  to smp_affinity.
> 
> picture looks liks this:
> 0-3 CPU get over 50% SI.... bandwith up.... 55% SI... bandwith up... 
> 100% SI on CPU0....
> 
> I remember patch to fix problem like it... patched function 
> e1000_clean...  kernel on pc have this patch (2.6.24-rc7-git2)... e1000 
> driver work much better (i up to 1.5-2x bandwidth before i get 100% SI), 
> but i think that it not get 100% that it can =)

If some patch works for you, and you can show here its advantages,
you should probably add here some link and request for merging.

BTW, I wonder if you tried to check if changing CONFIG_HZ makes any
difference here?

Regards,
Jarek P.
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