From: Alexander Viro <viro@math.psu.edu>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [Ext2-devel] disk throughput
Date: Mon, 5 Nov 2001 22:02:35 -0500 (EST) [thread overview]
Message-ID: <Pine.GSO.4.21.0111052132360.27563-100000@weyl.math.psu.edu> (raw)
In-Reply-To: <Pine.LNX.4.33.0111051748250.1710-100000@penguin.transmeta.com>
On Mon, 5 Nov 2001, Linus Torvalds wrote:
> And you have to realize that _whatever_ we do, it will always be a
> heuristic. We don't know what the right behaviour is without being able to
> predict the future. Agreed?
No arguments. While we are at it, let's just state once and forever:
FFS allocator sucks for fast-growth case
Everyone agrees with that, including me, you _and_ Kirk.
> The question is: "what can we do to improve it?". Not "what arguments can
> we come up with to make excuses for a sucky algorithm that clearly does
> the wrong thing for real-life loads".
Obviously.
> One such improvement has already been put on the table: remove the
> algorithm, and make it purely greedy.
>
> We know that works. And yes, we realize that it has downsides too. Which
> is why some kind of hybrid is probably called for. Come up with your own
Exactly.
> And maybe the fundamental problem is exactly that: because we're stuck
> with our decision forever, people felt that they couldn't afford to risk
> doing what was very obviously the right thing.
>
> So I still claim that we should look for short-time profit, and then try
> to fix up the problems longer term. With, if required, some kind of
> rebalancing.
Whatever heuristics we use, it _must_ catch fast-growth scenario. No
arguments on that. The question being, what will minimize the problems
for other cases.
On-line defrag can be actually fairly nasty - that had been tried and
it ends up with a hell of tricky details. Especially with page cache
in the game. And "umount once a month" is not serious - think of a
_large_ disk on a department NFS server. So I'd rather look for decent
heuristics before going for "let's defrag it once in a while" kind of
solution.
I definitely want to start with looking through relevant work - both
for the data and for information on _failed_ attempts to solve the
problem.
/me goes to dig through that stuff
next prev parent reply other threads:[~2001-11-06 3:03 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-11-05 2:13 disk throughput Andrew Morton
2001-11-05 3:20 ` Mohammad A. Haque
2001-11-05 3:31 ` Andrew Morton
2001-11-05 3:32 ` [Ext2-devel] " Mike Fedyk
2001-11-05 3:45 ` Andrew Morton
2001-11-05 4:39 ` Mike Fedyk
2001-11-05 7:06 ` Jens Axboe
2001-11-05 7:14 ` Andrew Morton
2001-11-05 7:26 ` Jens Axboe
2001-11-05 7:14 ` Mike Fedyk
2001-11-05 7:18 ` Jens Axboe
2001-11-05 7:18 ` Jens Axboe
2001-11-05 9:14 ` Mike Fedyk
2001-11-05 9:20 ` Jens Axboe
2001-11-05 5:54 ` Albert D. Cahalan
2001-11-05 8:04 ` Andrew Morton
2001-11-05 12:28 ` Matthias Andree
2001-11-05 14:23 ` Alexander Viro
2001-11-05 22:22 ` Andrew Morton
2001-11-05 22:41 ` Andreas Dilger
2001-11-05 22:53 ` Andrew Morton
2001-11-08 15:28 ` Constantin Loizides
2001-11-05 23:14 ` Dan Hollis
2001-11-06 10:52 ` Daniel Phillips
2001-11-06 16:17 ` Jeremy Fitzhardinge
2001-11-08 15:24 ` Constantin Loizides
2001-11-08 16:46 ` Jeremy Fitzhardinge
2001-11-09 6:08 ` Andrew Morton
2001-11-09 8:49 ` Jeremy Fitzhardinge
2001-11-06 21:45 ` Stephen Tweedie
2001-11-05 20:16 ` Andreas Dilger
2001-11-05 20:28 ` m
2001-11-05 21:39 ` Andrew Morton
2001-11-05 22:59 ` Linus Torvalds
2001-11-05 23:36 ` Alexander Viro
2001-11-05 23:50 ` Linus Torvalds
2001-11-06 0:03 ` Linus Torvalds
2001-11-06 1:33 ` Alexander Viro
2001-11-06 2:10 ` Linus Torvalds
2001-11-06 3:02 ` Alexander Viro [this message]
2001-11-06 8:39 ` Alan Cox
2001-11-06 8:37 ` Alexander Viro
2001-11-06 8:48 ` Andrew Morton
2001-11-06 3:49 ` Alexander Viro
2001-11-06 4:01 ` Linus Torvalds
2001-11-06 4:21 ` Alexander Viro
2001-11-06 5:01 ` Linus Torvalds
2001-11-06 5:31 ` Andrew Morton
2001-11-06 5:48 ` Linus Torvalds
2001-11-06 7:34 ` Mike Castle
2001-11-06 7:10 ` Kai Henningsen
2001-11-09 22:35 ` Riley Williams
2001-11-06 1:28 ` Alexander Viro
2001-11-06 9:16 ` Wojtek Pilorz
2001-11-06 9:58 ` Alexander Viro
2001-11-08 12:51 ` Pavel Machek
2001-11-06 21:48 ` Stephen Tweedie
2001-11-06 23:17 ` ext2/ialloc.c cleanup Alexander Viro
2001-11-07 19:34 ` [Ext2-devel] " Andreas Dilger
2001-11-07 20:02 ` Alexander Viro
2001-11-08 2:06 ` Andrew Morton
2001-11-08 20:45 ` Andrew Morton
2001-11-08 22:16 ` Alexander Viro
2001-11-08 22:43 ` Andreas Dilger
2001-11-08 23:08 ` Alexander Viro
2001-11-09 6:15 ` Andrew Morton
2001-11-09 6:56 ` Andreas Dilger
2001-11-09 7:09 ` Andrew Morton
2001-11-09 7:12 ` Alexander Viro
2001-11-09 7:18 ` Andrew Morton
2001-11-05 9:45 ` [Ext2-devel] disk throughput Alex Bligh - linux-kernel
2001-11-05 9:58 ` Alex Bligh - linux-kernel
2001-11-05 8:47 ` Jan Kara
2001-11-05 8:50 ` [Ext2-devel] " Mike Fedyk
2001-11-05 9:01 ` Jan Kara
2001-11-05 12:23 ` Matthias Andree
2001-11-05 22:39 ` Andrew Morton
2001-11-05 23:41 ` Matthias Andree
2001-11-12 6:04 [Ext2-devel] " Yan, Noah
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