linux-kernel - Re: PATCH: Allow over-ride of smp_found

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Date:	Fri, 6 Feb 2009 20:31:21 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Ben Greear <greearb@...delatech.com>,
	Thomas Gleixner <tglx@...utronix.de>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>, len.brown@...el.com
Subject: Re: PATCH:  Allow over-ride of smp_found_cfg with kernel cmd-line
	option.


* Ben Greear <greearb@...delatech.com> wrote:

> Allow user to keep smp_found_cfg set to 1 even if MADT
> cannot be parsed.  This works around funky BIOS on FWA-7304
> (VIA CN700 chipset) system, and possibly other systems as well.
> Without this override, performance drops by around 15% on
> network throughput tests on this system.

The question is, _why_ does network performance drop?

Do you have a before/after pair of /proc/interrupts output
perhaps? Does the layout of IRQs change?

The system is not SMP - so only something about UP-IOAPIC can
be helpful to performance here - or some unknown effect.

	Ingo
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