Subject: Re: [2.6.18-rc7-mm1] slow boot
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Andrew Morton <akpm@osdl.org>
Cc: Tilman Schmidt <tilman@imap.cc>, linux-kernel@vger.kernel.org,
       Chris Mason <mason@suse.com>, ext2-devel@lists.sourceforge.net,
       reiserfs-dev@namesys.com
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	 <20060924145337.ae152efd.akpm@osdl.org>
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Date: Sun, 24 Sep 2006 23:36:41 +0100
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Ar Sul, 2006-09-24 am 14:53 -0700, ysgrifennodd Andrew Morton:
> I've *never* seen any reports of any problems being caused by disk
> writeback caching.  Yes, it's a theoretical problem but for some reason it
> just doesn't seem to be a problem in practice.  Hence I'm really reluctant
> to go and slow everyone's machines down so much in this manner.

It happens in some cases, the usual one is sudden loss of power. In the
crashed box cases the disk still gets to write data back and in the
Linux power off sanely cases we explicitly cache flush. Its the sudden
loss of power case that is nasty.

We are also helped of course by the fact the cache is never more than
can be flushed in about 7 seconds because of other-os features.

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