linux-kernel - Re: [ext3][kernels >= 2.6.20.7 at least] KDE going comatose when FS is under heavy write load (massive starvation)

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Message-ID: <alpine.LFD.0.98.0704271420390.9964@woody.linux-foundation.org>
Date:	Fri, 27 Apr 2007 14:22:48 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
cc:	Mike Galbraith <efault@....de>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jens Axboe <jens.axboe@...cle.com>
Subject: Re: [ext3][kernels >= 2.6.20.7 at least] KDE going comatose when FS
 is under heavy write load (massive starvation)



On Fri, 27 Apr 2007, Jan Engelhardt wrote:
> 
> Interesting. For my laptop, I have configured like 90 for
> dirty_background_ratio and 95 for dirty_ratio. Makes for a nice
> delayed write, but I do not do workloads bigger than extracing kernel
> tarballs (~250 MB) and coding away on that machine (488 MB RAM) anyway.
> Setting it to something like 95, I could probably rm -Rf the kernel
> tree again and the disk never gets active because it is all cached.
> But if dirty_ratio is lowered, the disk will get active soon.

Yes. For laptops, you may want to
 - raise the dirty limits
 - increase the dirty scan times

but you do realize that if you then need memory for something else, 
latency just becomes *horrible*. So even on laptops, it's not obviously 
the right thing to do (these days, throwing money at the problem instead, 
and getting one of the nice new 1.8" flash disks, will solve all issues: 
you'd have no reason to try to delay spinning up the disk anyway).

		Linus
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