linux-kernel - Re: irqpoll kernel option hurts performance?

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Date:	Fri, 03 Nov 2006 16:00:58 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	xp newbie <xp_newbie@...oo.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: irqpoll kernel option hurts performance?

Ar Gwe, 2006-11-03 am 07:10 -0800, ysgrifennodd xp newbie:
> Thank you, Alan. Indeed, it is a desktop machine so I
> guess I should not be too concerned. I should note
> hoever that while downloading an ISO image from the
> Internet and doing nothing else (not even moving the
> mouse), the System Monitor showed CPU usage of 15%.
> The same machine booting to Windows 2000, shows in
> such circumstances 0% CPU use (something lesser than
> 1% to be more exact).

The two systems don't measure performance the same way. That makes
comparisons using their own monitoring tools a bit dubious and can make
either OS look better in cases where it isn't

> But that board, again, was running Windows 2000
> without any performance sacrifices... How does Windows
> achieve that trick?

I wish I knew. One possibility - especially as this appears to be the
USB 2.0 is that it provides different rules for different OS's (thats
intended to be a feature so it can hide EHCI from old windows etc)

You might want to see if booting with the kernel option	"acpi_noirq" has
any effect for the better, you can also spoof different versions of
windows for ACPI using

	acpi_os_name="Microsoft Windows"

(Not sure how you spoof XP etc offhand but it should be documented
somewhere)

Various things are going on to improve the poor state of PC BIOSes
including a firmware test kit from Intel.

> I know that there is an issue with Promise
> controllers, as Promise releases only binaries of its
> drivers for Linux, not the source code. :(

Actually promise are generally providing both docs and their own binary
driver. 

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