linux-kernel - Re: [Patch] document ext3 requirements (was Re: [RFD] Incremental fsck)

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Message-ID: <20080119145111.GF24512@elf.ucw.cz>
Date:	Sat, 19 Jan 2008 15:51:11 +0100
From:	Pavel Machek <pavel@....cz>
To:	Valdis.Kletnieks@...edu
Cc:	Daniel Phillips <phillips@...gle.com>, David Chinner <dgc@....com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Theodore Tso <tytso@....edu>, Al Boldi <a1426z@...ab.com>,
	Valerie Henson <val.henson@...il.com>,
	Rik van Riel <riel@...hat.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Patch] document ext3 requirements (was Re: [RFD] Incremental
	fsck)

Hi!

> > I guess I should try to measure it. (Linux already does writeback
> > caching, with 2GB of memory. I wonder how important disks's 2MB of
> > cache can be).
> 
> It serves essentially the same purpose as the 'async' option in /etc/exports
> (i.e. we declare it "done" when the other end of the wire says it's caught
> the data, not when it's actually committed), with similar latency wins.  Of
> course, it's impedance-matching for bursty traffic - the 2M doesn't do much
> at all if you're streaming data to it.  For what it's worth, the 80G Seagate
> drive in my laptop claims it has 8M, so it probably does 4 times as much
> good as 2M. ;)

I doubt "impedance-matching" is useful here. SATA link is fast/low
latency, and kernel already does buffering with main memory...

Hmm... what is the way to measure that? Tar decompress kernel few
times with cache on / cache off?
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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