From: Andrew Morton <akpm@linux-foundation.org>
To: David Chinner <dgc@sgi.com>
Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru>,
Christoph Lameter <clameter@sgi.com>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Mel Gorman <mel@skynet.ie>,
andi@firstfloor.org, Rik van Riel <riel@redhat.com>,
Pekka Enberg <penberg@cs.helsinki.fi>,
mpm@selenic.com
Subject: Re: [patch 10/21] buffer heads: Support slab defrag
Date: Tue, 20 May 2008 16:28:16 -0700 [thread overview]
Message-ID: <20080520162816.e5dfeffa.akpm@linux-foundation.org> (raw)
In-Reply-To: <20080520231942.GX103491721@sgi.com>
On Wed, 21 May 2008 09:19:42 +1000 David Chinner <dgc@sgi.com> wrote:
> sync_inode() is far too
> heavy-weight to be used in a reclaim context
It's more than efficiency. There are lots and lots of things we cannot
do in direct-reclaim context.
a) Can't lock pages (well we kinda sorta could, but generally code
will just trylock)
b) Cannot rely on the inode or the address_space being present in
memory after we have unlocked the page.
c) Cannot run iput(). Or at least, we couldn't five or six years
ago. afaik nobody has investigated whether the situation is now
better or worse.
d) lots of deadlock scenarios - need to test __GFP_FS basically everywhere
in which you share code with normal writeback paths.
Plus e), f), g) and h). Direct-reclaim is a hostile environment.
Things like b) are a real killer - nasty, subtle, rare,
memory-pressure-dependent crashes.
next prev parent reply other threads:[~2008-05-20 23:44 UTC|newest]
Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-10 3:08 [patch 00/21] Slab Fragmentation Reduction V12 Christoph Lameter
2008-05-10 3:08 ` [patch 01/21] slub: Add defrag_ratio field and sysfs support Christoph Lameter
2008-05-10 3:08 ` [patch 02/21] slub: Replace ctor field with ops field in /sys/slab/* Christoph Lameter
2008-05-10 3:08 ` [patch 03/21] slub: Add get() and kick() methods Christoph Lameter
2008-05-10 3:08 ` [patch 04/21] slub: Sort slab cache list and establish maximum objects for defrag slabs Christoph Lameter
2008-05-10 3:08 ` [patch 05/21] slub: Slab defrag core Christoph Lameter
2008-05-10 3:08 ` [patch 06/21] slub: Add KICKABLE to avoid repeated kick() attempts Christoph Lameter
2008-05-10 3:08 ` [patch 07/21] slub: Extend slabinfo to support -D and -F options Christoph Lameter
2008-05-10 3:08 ` [patch 08/21] slub: add defrag statistics Christoph Lameter
2008-05-10 3:08 ` [patch 09/21] slub: Trigger defragmentation from memory reclaim Christoph Lameter
2008-05-10 3:08 ` [patch 10/21] buffer heads: Support slab defrag Christoph Lameter
2008-05-12 0:24 ` David Chinner
2008-05-15 17:42 ` Christoph Lameter
2008-05-15 23:10 ` David Chinner
2008-05-16 17:01 ` Christoph Lameter
2008-05-19 5:45 ` David Chinner
2008-05-19 16:44 ` Christoph Lameter
2008-05-20 0:25 ` David Chinner
2008-05-20 6:56 ` Evgeniy Polyakov
2008-05-20 21:46 ` David Chinner
2008-05-20 22:25 ` Evgeniy Polyakov
2008-05-20 23:19 ` David Chinner
2008-05-20 23:28 ` Andrew Morton [this message]
2008-05-21 6:15 ` Evgeniy Polyakov
2008-05-21 6:24 ` Andrew Morton
2008-05-21 17:52 ` iput() in reclaim context Hugh Dickins
2008-05-21 17:58 ` Evgeniy Polyakov
2008-05-21 18:12 ` Andrew Morton
2008-05-20 23:22 ` [patch 10/21] buffer heads: Support slab defrag Evgeniy Polyakov
2008-05-20 23:30 ` David Chinner
2008-05-21 6:20 ` Evgeniy Polyakov
2008-05-21 1:56 ` Christoph Lameter
2008-05-20 22:53 ` Jamie Lokier
2008-05-10 3:08 ` [patch 11/21] inodes: Support generic defragmentation Christoph Lameter
2008-05-10 3:08 ` [patch 12/21] Filesystem: Ext2 filesystem defrag Christoph Lameter
2008-05-10 3:08 ` [patch 13/21] Filesystem: Ext3 " Christoph Lameter
2008-05-10 3:08 ` [patch 14/21] Filesystem: Ext4 " Christoph Lameter
2008-05-10 3:08 ` [patch 15/21] Filesystem: XFS slab defragmentation Christoph Lameter
2008-05-10 6:55 ` Christoph Hellwig
2008-05-10 3:08 ` [patch 16/21] Filesystem: /proc filesystem support for slab defrag Christoph Lameter
2008-05-10 3:08 ` [patch 17/21] Filesystem: Slab defrag: Reiserfs support Christoph Lameter
2008-05-10 3:08 ` [patch 18/21] Filesystem: Socket inode defragmentation Christoph Lameter
2008-05-13 13:28 ` Evgeniy Polyakov
2008-05-15 17:40 ` Christoph Lameter
2008-05-15 18:23 ` Evgeniy Polyakov
2008-05-10 3:08 ` [patch 19/21] dentries: Add constructor Christoph Lameter
2008-05-10 3:08 ` [patch 20/21] dentries: dentry defragmentation Christoph Lameter
2008-05-10 3:08 ` [patch 21/21] slab defrag: Obsolete SLAB Christoph Lameter
2008-05-10 9:53 ` Andi Kleen
2008-05-11 2:15 ` Rik van Riel
2008-05-12 7:38 ` KOSAKI Motohiro
2008-05-12 7:54 ` Pekka Enberg
2008-05-12 10:08 ` Andi Kleen
2008-05-12 10:23 ` Pekka Enberg
2008-05-14 17:30 ` Christoph Lameter
2008-05-14 17:29 ` Christoph Lameter
2008-05-14 17:49 ` Andi Kleen
2008-05-14 18:03 ` Christoph Lameter
2008-05-14 18:18 ` Matt Mackall
2008-05-14 19:21 ` Christoph Lameter
2008-05-14 19:49 ` Matt Mackall
2008-05-14 20:33 ` Christoph Lameter
2008-05-14 21:02 ` Matt Mackall
2008-05-14 21:26 ` Christoph Lameter
2008-05-14 21:54 ` Matt Mackall
2008-05-15 17:15 ` Christoph Lameter
2008-05-15 3:26 ` Zhang, Yanmin
2008-05-15 17:05 ` Christoph Lameter
2008-05-15 17:49 ` Matthew Wilcox
2008-05-15 17:58 ` Christoph Lameter
2008-05-15 18:13 ` Matthew Wilcox
2008-05-15 18:43 ` Christoph Lameter
2008-05-15 18:51 ` Matthew Wilcox
2008-05-15 19:09 ` Christoph Lameter
2008-05-15 19:29 ` Matthew Wilcox
2008-05-15 20:14 ` Matthew Wilcox
2008-05-15 20:30 ` Pekka Enberg
2008-05-16 19:17 ` Christoph Lameter
2008-05-16 19:06 ` Christoph Lameter
2008-05-15 18:19 ` Eric Dumazet
2008-05-15 18:29 ` Vegard Nossum
2008-05-16 5:16 ` Zhang, Yanmin
2008-05-14 18:05 ` Christoph Lameter
2008-05-14 20:46 ` Christoph Lameter
2008-05-14 20:58 ` Matthew Wilcox
2008-05-14 21:00 ` Christoph Lameter
2008-05-14 21:21 ` Matthew Wilcox
2008-05-14 21:33 ` Christoph Lameter
2008-05-14 21:43 ` Matthew Wilcox
2008-05-14 21:53 ` Christoph Lameter
2008-05-14 22:00 ` Matthew Wilcox
2008-05-14 22:32 ` Christoph Lameter
2008-05-14 22:34 ` Christoph Lameter
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