netdev - Re: [PATCH] Re: Bad network performance over 2Gbps

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Date:	Mon, 21 Apr 2008 21:52:00 +0200 (CEST)
From:	Bodo Eggert <7eggert@....de>
To:	Rick Jones <rick.jones2@...com>
cc:	7eggert@....de, Kok@...r.kernel.org,
	Auke <auke-jan.h.kok@...el.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Anton Titov <a.titov@...t.bg>, Chris Snook <csnook@...hat.com>,
	"H. Willstrand" <h.willstrand@...il.com>, netdev@...r.kernel.org,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] Re: Bad network performance over 2Gbps

On Mon, 21 Apr 2008, Rick Jones wrote:
> Bodo Eggert wrote:
> > Kok, Auke <auke-jan.h.kok@...el.com> wrote:

> > > [X86] IRQBALANCE: Mark as BROKEN and disable by default
> > > 
> > > The IRQBALANCE option causes interrupts to bounce all around on SMP
> > > systems
> > > quickly burying the CPU in migration cost and cache misses. Mainly
> > > affected
> > > are network interrupts and this results in one CPU pegged in softirqd
> > > completely.
> > 
> > 
> > If this is the problem, maybe it would help to only balance the IRQs each
> > e.g. ten seconds? Unfortunately I have no SMP system to try it out.
> 
> Be it kernel or user space, for consistent benchmark results it needs to be
> able to be turned-off without turning the code.  That leaves me in agreement
> with Stephen that if it must exist, the user space one would be preferable.
> It can be easily terminated with extreme prejudice.

I agree that having a full-featured userspace balancer daemon with lots of 
intelligence will be theoretically better, but if you can have a simple
daemon doing OK on many machines for less than the userspace daemon's
kernel stack, why not?
-- 
Funny quotes:
31. Why do "overlook" and "oversee" mean opposite things?
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