netdev - Re: [PATCH] rps: make distributing packets fairly among all the online CPUs default

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Message-ID: <874ok7dtg4.fsf@basil.nowhere.org>
Date:	Tue, 23 Mar 2010 15:05:31 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Changli Gao <xiaosuo@...il.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Tom Herbert <therbert@...gle.com>, netdev@...r.kernel.org,
	Ben Hutchings <bhutchings@...arflare.com>
Subject: Re: [PATCH] rps: make distributing packets fairly among all the  online CPUs default

Changli Gao <xiaosuo@...il.com> writes:
>
> I do think distributing packets fairly among all the online CPUs will
> helps most of users. I remember the smp_affinity of IRQ is the
> online_cpu_mask be default.

The established wisdom is that most apps prefer locality.

The cost of data transfer between CPUs is worse than the 
overhead of processing the packet header in the stack.

That's why no system does interrupt RR by default anymore.

Besides if you do such a change you would need extensive benchmarking
to verify that it's a good idea.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
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