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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Benjamin LaHaise <bcrl@kvack.org>
Cc: Jiri Slaby <jirislaby@gmail.com>, Uwe Bugla <uwe.bugla@gmx.de>,
	akpm@linux-foundation.org, bunk@stusta.de,
	linux-kernel@vger.kernel.org,
	Stephane Eranian <eranian@hpl.hp.com>, Andi Kleen <ak@suse.de>
Subject: Re: bug in kernel 2.6.21-rc1-git1: conventional floppy drive cannot be mounted without hanging up the whole system
Date: Mon, 26 Feb 2007 09:10:22 -0800 (PST)	[thread overview]
Message-ID: <Pine.LNX.4.64.0702260906540.12485@woody.linux-foundation.org> (raw)
In-Reply-To: <20070226163429.GL26583@kvack.org>



On Mon, 26 Feb 2007, Benjamin LaHaise wrote:
> 
> Side note: this patch adds several function calls (4), several additional 
> L1 cache touches and a generally inefficient code path to *every single 
> interrupt that exits from the idle poll*, not to mention the extra (useless, 
> as it doesn't get used on 99.9% of deployed systems) function call and cache 
> touches to every single interrupt.

It is in fact possible that the floppy failure might just be from some 
timing-dependent thing, and the slowdown itself is the problem.

Although I do find that a bit unlikely, since machines these days are 
about a million times faster than they used to be, so even if it's 
unnecessarily slow, it shouldn't be noticeable for a floppy drive.

>  Keep in mind that systems acting as routers will often be sitting in 
> the idle loop when processing interrupts.  At the very least this 
> overhead (which is noticable on profiles) should be configurable.  I 
> don't think that my 586 class embedded routers really need this crap to 
> be going into the kernel.

I'm inclined to agree. Considering that the patch is known to cause 
problems, and that it's apparently broken on x86 *anyway* (the 
idle_notifier_register function isn't even exported), and considering that 
it's clearly bad for interrupt performance and could have been done a lot 
better, I would suggest just ripping it all out.

And I think we should do the same for x86-64 too..

		Linus

  reply	other threads:[~2007-02-26 17:20 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-24 17:54 Uwe Bugla
2007-02-24 18:07 ` Andrew Morton
2007-02-24 18:29   ` Uwe Bugla
2007-02-24 19:23   ` Uwe Bugla
2007-02-24 19:49     ` Ray Lee
2007-02-26 10:38 ` Jiri Slaby
2007-02-26 15:12   ` Jiri Slaby
2007-02-26 15:51     ` Linus Torvalds
2007-02-26 16:28       ` Jiri Slaby
2007-02-26 16:34       ` Benjamin LaHaise
2007-02-26 17:10         ` Linus Torvalds [this message]
2007-02-26 17:45           ` Stephane Eranian
2007-02-26 17:28       ` Stephane Eranian
2007-02-26 17:37         ` Linus Torvalds
2007-02-25 18:29 Uwe Bugla
2007-02-25 21:04 ` Alexey Dobriyan
2007-02-26  3:55 ` Mike Galbraith
2007-02-26 18:06 Oleg Nesterov
2007-02-26 18:13 ` Linus Torvalds
2007-02-26 20:55   ` Rene Herman
2007-02-26 21:14     ` Linus Torvalds
2007-02-28  2:42       ` Bill Davidsen
2007-02-28 13:04         ` Alan
2007-02-28 12:20           ` Rene Herman

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