netdev - Re: [PATCH v6] net: batch skb dequeueing from softnet input_pkt

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Message-ID: <20100502215450.GC2673@gargoyle.fritz.box>
Date:	Sun, 2 May 2010 23:54:50 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, hadi@...erus.ca,
	xiaosuo@...il.com, therbert@...gle.com, shemminger@...tta.com,
	netdev@...r.kernel.org, lenb@...nel.org, arjan@...radead.org
Subject: Re: [PATCH v6] net: batch skb dequeueing from softnet
	input_pkt_queue

On Sun, May 02, 2010 at 11:45:55PM +0200, Eric Dumazet wrote:
> Le dimanche 02 mai 2010 à 23:25 +0200, Andi Kleen a écrit :
> 
> > It's pointless to send an IPI to your thread sibling for this. 
> > Everything it could do you can do yourself too with the same performance.
> > 
> > -Andi
> 
> Amen

That is in terms of cache locality.

> 
> Tests just prove the reverse.

What do you mean? 

> 
> I have some collegues that disable HyperThreading for exact same
> reasons. I wonder why Intel designed HT. Should be marketing I guess.

HT (especially Nehalem HT) is useful for a wide range of workloads.
Just handling network interrupts for its thread sibling is not one of them.

-Andi

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