From: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: David Chinner <dgc@sgi.com>, 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: Wed, 21 May 2008 10:15:32 +0400 [thread overview]
Message-ID: <20080521061531.GA27362@2ka.mipt.ru> (raw)
In-Reply-To: <20080520162816.e5dfeffa.akpm@linux-foundation.org>
On Tue, May 20, 2008 at 04:28:16PM -0700, Andrew Morton (akpm@linux-foundation.org) wrote:
> 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.
Which basically means we can not do direct writeback at reclaim time?..
--
Evgeniy Polyakov
next prev parent reply other threads:[~2008-05-21 6:15 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
2008-05-21 6:15 ` Evgeniy Polyakov [this message]
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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