netdev - Re: [PATCH net-next-2.6] net: Xmit Packet Steering (XPS)

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Message-ID: <4B078F99.70100@gmail.com>
Date:	Sat, 21 Nov 2009 07:58:33 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tom Herbert <therbert@...gle.com>
CC:	Andi Kleen <andi@...stfloor.org>,
	"David S. Miller" <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next-2.6] net: Xmit Packet Steering (XPS)

Tom Herbert a écrit :
> 
> It probably is a special case, but addresses a real problem.  Like rps,
> this addresses the case where a single queue NIC is the bottleneck on a
> system.  Anything that takes work off the interrupting core and spreads
> it to other cores may alleviate the bottleneck. 
> 


Yes, and this brings back an idea I mentioned earlier in April, for a multicast
problem we had with AthenaCR.

XPS could be 'started' only if caller runs from ksoftirqd, eg we are in a stress
situation, and additional cost of XPS is nothing compared to huge gains we have
to spread part of work to more CPUS.

(Costs of XPS includes : ~500 bytes of ICACHE, and IPI)


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