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From: Andrew Morton <akpm@osdl.org>
To: Christoph Lameter <clameter@sgi.com>
Cc: menage@google.com, linux-kernel@vger.kernel.org,
	nickpiggin@yahoo.com.au, linux-mm@kvack.org, ak@suse.de,
	pj@sgi.com, dgc@sgi.com
Subject: Re: [RFC 0/8] Cpuset aware writeback
Date: Tue, 16 Jan 2007 23:00:34 -0800	[thread overview]
Message-ID: <20070116230034.b8cb4263.akpm@osdl.org> (raw)
In-Reply-To: <Pine.LNX.4.64.0701162219180.5215@schroedinger.engr.sgi.com>

> On Tue, 16 Jan 2007 22:27:36 -0800 (PST) Christoph Lameter <clameter@sgi.com> wrote:
> On Tue, 16 Jan 2007, Andrew Morton wrote:
> 
> > > Yes this is the result of the hierachical nature of cpusets which already 
> > > causes issues with the scheduler. It is rather typical that cpusets are 
> > > used to partition the memory and cpus. Overlappig cpusets seem to have 
> > > mainly an administrative function. Paul?
> > 
> > The typical usage scenarios don't matter a lot: the examples I gave show
> > that the core problem remains unsolved.  People can still hit the bug.
> 
> I agree the overlap issue is a problem and I hope it can be addressed 
> somehow for the rare cases in which such nesting takes place.
> 
> One easy solution may be to check the dirty ratio before engaging in 
> reclaim. If the dirty ratio is sufficiently high then trigger writeout via 
> pdflush (we already wakeup pdflush while scanning and you already noted 
> that pdflush writeout is not occurring within the context of the current 
> cpuset) and pass over any dirty pages during LRU scans until some pages 
> have been cleaned up.
> 
> This means we allow allocation of additional kernel memory outside of the 
> cpuset while triggering writeout of inodes that have pages on the nodes 
> of the cpuset. The memory directly used by the application is still 
> limited. Just the temporary information needed for writeback is allocated 
> outside.

Gad.  None of that should be necessary.

> Well sounds somehow still like a hack. Any other ideas out there?

Do what blockdevs do: limit the number of in-flight requests (Peter's
recent patch seems to be doing that for us) (perhaps only when PF_MEMALLOC
is in effect, to keep Trond happy) and implement a mempool for the NFS
request critical store.  Additionally:

- we might need to twiddle the NFS gfp_flags so it doesn't call the
  oom-killer on failure: just return NULL.

- consider going off-cpuset for critical allocations.  It's better than
  going oom.  A suitable implementation might be to ignore the caller's
  cpuset if PF_MEMALLOC.  Maybe put a WARN_ON_ONCE in there: we prefer that
  it not happen and we want to know when it does.



btw, regarding the per-address_space node mask: I think we should free it
when the inode is clean (!mapping_tagged(PAGECACHE_TAG_DIRTY)).  Chances
are, the inode will be dirty for 30 seconds and in-core for hours.  We
might as well steal its nodemask storage and give it to the next file which
gets written to.  A suitable place to do all this is in
__mark_inode_dirty(I_DIRTY_PAGES), using inode_lock to protect
address_space.dirty_page_nodemask.

  reply	other threads:[~2007-01-17  7:00 UTC|newest]

Thread overview: 110+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-16  5:47 Christoph Lameter
2007-01-16  5:47 ` [RFC 1/8] Convert higest_possible_node_id() into nr_node_ids Christoph Lameter
2007-01-16 22:05   ` Andi Kleen
2007-01-17  3:14     ` Christoph Lameter
2007-01-17  4:15       ` Andi Kleen
2007-01-17  4:23         ` Christoph Lameter
2007-01-16  5:47 ` [RFC 2/8] Add a map to inodes to track dirty pages per node Christoph Lameter
2007-01-16  5:47 ` [RFC 3/8] Add a nodemask to pdflush functions Christoph Lameter
2007-01-16  5:48 ` [RFC 4/8] Per cpuset dirty ratio handling and writeout Christoph Lameter
2007-01-16  5:48 ` [RFC 5/8] Make writeout during reclaim cpuset aware Christoph Lameter
2007-01-16 22:07   ` Andi Kleen
2007-01-17  4:20     ` Paul Jackson
2007-01-17  4:28       ` Andi Kleen
2007-01-17  4:36         ` Paul Jackson
2007-01-17  5:59           ` Andi Kleen
2007-01-17  6:19             ` Christoph Lameter
2007-01-17  4:23     ` Christoph Lameter
2007-01-16  5:48 ` [RFC 6/8] Throttle vm writeout per cpuset Christoph Lameter
2007-01-16  5:48 ` [RFC 7/8] Exclude unreclaimable pages from dirty ration calculation Christoph Lameter
2007-01-18 15:48   ` Nikita Danilov
2007-01-18 19:56     ` Christoph Lameter
2007-01-16  5:48 ` [RFC 8/8] Reduce inode memory usage for systems with a high MAX_NUMNODES Christoph Lameter
2007-01-16 19:52   ` Paul Menage
2007-01-16 20:00     ` Christoph Lameter
2007-01-16 20:06       ` Paul Menage
2007-01-16 20:51         ` Christoph Lameter
2007-01-16  7:38 ` [RFC 0/8] Cpuset aware writeback Peter Zijlstra
2007-01-16 20:10   ` Christoph Lameter
2007-01-16  9:25 ` Paul Jackson
2007-01-16 17:13   ` Christoph Lameter
2007-01-16 21:53 ` Andrew Morton
2007-01-16 22:08   ` [PATCH] nfs: fix congestion control Peter Zijlstra
2007-01-16 22:27     ` Trond Myklebust
2007-01-17  2:41       ` Peter Zijlstra
2007-01-17  6:15         ` Trond Myklebust
2007-01-17  8:49           ` Peter Zijlstra
2007-01-17 13:50             ` Trond Myklebust
2007-01-17 14:29               ` Peter Zijlstra
2007-01-17 14:45                 ` Trond Myklebust
2007-01-17 20:05     ` Christoph Lameter
2007-01-17 21:52       ` Peter Zijlstra
2007-01-17 21:54         ` Trond Myklebust
2007-01-18 13:27           ` Peter Zijlstra
2007-01-18 15:49             ` Trond Myklebust
2007-01-19  9:33               ` Peter Zijlstra
2007-01-19 13:07                 ` Peter Zijlstra
2007-01-19 16:51                   ` Trond Myklebust
2007-01-19 17:54                     ` Peter Zijlstra
2007-01-19 17:20                   ` Christoph Lameter
2007-01-19 17:57                     ` Peter Zijlstra
2007-01-19 18:02                       ` Christoph Lameter
2007-01-19 18:26                       ` Trond Myklebust
2007-01-19 18:27                         ` Christoph Lameter
2007-01-20  7:01                         ` [PATCH] nfs: fix congestion control -v3 Peter Zijlstra
2007-01-22 16:12                           ` Trond Myklebust
2007-01-25 15:32                             ` [PATCH] nfs: fix congestion control -v4 Peter Zijlstra
2007-01-26  5:02                               ` Andrew Morton
2007-01-26  8:00                                 ` Peter Zijlstra
2007-01-26  8:50                                   ` Peter Zijlstra
2007-01-26  5:09                               ` Andrew Morton
2007-01-26  5:31                                 ` Christoph Lameter
2007-01-26  6:04                                   ` Andrew Morton
2007-01-26  6:53                                     ` Christoph Lameter
2007-01-26  8:03                                     ` Peter Zijlstra
2007-01-26  8:51                                       ` Andrew Morton
2007-01-26  9:01                                         ` Peter Zijlstra
2007-02-20 12:59                                         ` Peter Zijlstra
2007-01-22 17:59                           ` [PATCH] nfs: fix congestion control -v3 Christoph Lameter
2007-01-17 23:15     ` [PATCH] nfs: fix congestion control Christoph Hellwig
2007-01-16 22:15   ` [RFC 0/8] Cpuset aware writeback Christoph Lameter
2007-01-16 23:40     ` Andrew Morton
2007-01-17  0:16       ` Christoph Lameter
2007-01-17  1:07         ` Andrew Morton
2007-01-17  1:30           ` Christoph Lameter
2007-01-17  2:34             ` Andrew Morton
2007-01-17  3:40               ` Christoph Lameter
2007-01-17  4:02                 ` Paul Jackson
2007-01-17  4:05                 ` Andrew Morton
2007-01-17  6:27                   ` Christoph Lameter
2007-01-17  7:00                     ` Andrew Morton [this message]
2007-01-17  8:01                       ` Paul Jackson
2007-01-17  9:57                         ` Andrew Morton
2007-01-17 19:43                       ` Christoph Lameter
2007-01-17 22:10                         ` Andrew Morton
2007-01-18  1:10                           ` Christoph Lameter
2007-01-18  1:25                             ` Andrew Morton
2007-01-18  5:21                               ` Christoph Lameter
2007-01-16 23:44   ` David Chinner
2007-01-16 22:01 ` Andi Kleen
2007-01-16 22:18   ` Christoph Lameter
2007-02-02  1:38 ` Ethan Solomita
2007-02-02  2:16   ` Christoph Lameter
2007-02-02  4:03     ` Andrew Morton
2007-02-02  5:29       ` Christoph Lameter
2007-02-02  6:02         ` Neil Brown
2007-02-02  6:17           ` Christoph Lameter
2007-02-02  6:41             ` Neil Brown
2007-02-02  7:12         ` Andrew Morton
2007-03-21 21:11     ` Ethan Solomita
2007-03-21 21:29       ` Christoph Lameter
2007-03-21 21:52         ` Andrew Morton
2007-03-21 21:57           ` Christoph Lameter
2007-04-19  2:07         ` Ethan Solomita
2007-04-19  2:55           ` Christoph Lameter
2007-04-19  7:52             ` Ethan Solomita
2007-04-19 16:03               ` Christoph Lameter
2007-04-21  1:37             ` Ethan Solomita
2007-04-21  1:48               ` Christoph Lameter
2007-04-21  8:15                 ` Ethan Solomita
2007-04-21 15:40                   ` Christoph Lameter

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