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From: Christoph Lameter <clameter@sgi.com>
To: Christian Bell <christian.bell@qlogic.com>
Cc: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
	Rik van Riel <riel@redhat.com>,
	Andrea Arcangeli <andrea@qumranet.com>,
	a.p.zijlstra@chello.nl, izike@qumranet.com,
	Roland Dreier <rdreier@cisco.com>,
	steiner@sgi.com, linux-kernel@vger.kernel.org, avi@qumranet.com,
	linux-mm@kvack.org, daniel.blueman@quadrics.com,
	Robin Holt <holt@sgi.com>,
	general@lists.openfabrics.org,
	Andrew Morton <akpm@linux-foundation.org>,
	kvm-devel@lists.sourceforge.net
Subject: Re: [ofa-general] Re: Demand paging for memory regions
Date: Wed, 13 Feb 2008 12:32:12 -0800 (PST)	[thread overview]
Message-ID: <Pine.LNX.4.64.0802131227200.20156@schroedinger.engr.sgi.com> (raw)
In-Reply-To: <20080213194621.GD19742@mv.qlogic.com>

On Wed, 13 Feb 2008, Christian Bell wrote:

> not always be in the thousands but you're still claiming scalability
> for a mechanism that essentially logs who accesses the regions.  Then
> there's the fact that reclaim becomes a collective communication
> operation over all region accessors.  Makes me nervous.

Well reclaim is not a very fast process (and we usually try to avoid it 
as much as possible for our HPC). Essentially its only there to allow 
shifts of processing loads and to allow efficient caching of application 
data.

> However, short of providing user-level notifications for pinned pages
> that are inadvertently released to the O/S, I don't believe that the
> patchset provides any significant added value for the HPC community
> that can't optimistically do RDMA demand paging.

We currently also run XPmem with pinning. Its great as long as you just 
run one load on the system. No reclaim ever iccurs.

However, if you do things that require lots of allocations etc etc then 
the page pinning can easily lead to livelock if reclaim is finally 
triggerd and also strange OOM situations since the VM cannot free any 
pages. So the main issue that is addressed here is reliability of pinned 
page operations. Better VM integration avoids these issues because we can 
unpin on request to deal with memory shortages.



  reply	other threads:[~2008-02-13 20:32 UTC|newest]

Thread overview: 81+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-08 22:06 [patch 0/6] MMU Notifiers V6 Christoph Lameter
2008-02-08 22:06 ` [patch 1/6] mmu_notifier: Core code Christoph Lameter
2008-02-08 22:06 ` [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges Christoph Lameter
2008-02-08 22:06 ` [patch 3/6] mmu_notifier: invalidate_page callbacks Christoph Lameter
2008-02-08 22:06 ` [patch 4/6] mmu_notifier: Skeleton driver for a simple mmu_notifier Christoph Lameter
2008-02-08 22:06 ` [patch 5/6] mmu_notifier: Support for drivers with revers maps (f.e. for XPmem) Christoph Lameter
2008-02-08 22:06 ` [patch 6/6] mmu_rmap_notifier: Skeleton for complex driver that uses its own rmaps Christoph Lameter
2008-02-08 22:23 ` [patch 0/6] MMU Notifiers V6 Andrew Morton
2008-02-08 23:32   ` Christoph Lameter
2008-02-08 23:36     ` Robin Holt
2008-02-08 23:41       ` Christoph Lameter
2008-02-08 23:43         ` Robin Holt
2008-02-08 23:56           ` Andrew Morton
2008-02-09  0:05             ` Christoph Lameter
2008-02-09  0:12               ` [ofa-general] " Roland Dreier
2008-02-09  0:16                 ` Christoph Lameter
2008-02-09  0:22                   ` Roland Dreier
2008-02-09  0:36                     ` Christoph Lameter
2008-02-09  1:24                       ` Andrea Arcangeli
2008-02-09  1:27                         ` Christoph Lameter
2008-02-09  1:56                           ` Andrea Arcangeli
2008-02-09  2:16                             ` Christoph Lameter
2008-02-09 12:55                               ` Rik van Riel
2008-02-09 21:46                                 ` Christoph Lameter
2008-02-11 22:40                                   ` Demand paging for memory regions (was Re: MMU Notifiers V6) Roland Dreier
2008-02-12 22:01                                     ` Steve Wise
2008-02-12 22:10                                       ` Christoph Lameter
2008-02-12 22:41                                         ` [ofa-general] Re: Demand paging for memory regions Roland Dreier
2008-02-12 23:14                                           ` Felix Marti
2008-02-13  0:57                                             ` Christoph Lameter
2008-02-14 15:09                                             ` Steve Wise
2008-02-14 15:53                                               ` Robin Holt
2008-02-14 16:23                                                 ` Steve Wise
2008-02-14 17:48                                                   ` Caitlin Bestler
2008-02-14 19:39                                               ` Christoph Lameter
2008-02-14 20:17                                                 ` Caitlin Bestler
2008-02-14 20:20                                                   ` Christoph Lameter
2008-02-14 22:43                                                     ` Caitlin Bestler
2008-02-14 22:48                                                       ` Christoph Lameter
2008-02-15  1:26                                                         ` Caitlin Bestler
2008-02-15  2:37                                                           ` Christoph Lameter
2008-02-15 18:09                                                             ` Caitlin Bestler
2008-02-15 18:45                                                               ` Christoph Lameter
2008-02-15 18:53                                                                 ` Caitlin Bestler
2008-02-15 20:02                                                                   ` Christoph Lameter
2008-02-15 20:14                                                                     ` Caitlin Bestler
2008-02-15 22:50                                                                       ` Christoph Lameter
2008-02-15 23:50                                                                         ` Caitlin Bestler
2008-02-12 23:23                                           ` Jason Gunthorpe
2008-02-13  1:01                                             ` Christoph Lameter
2008-02-13  1:26                                               ` Jason Gunthorpe
2008-02-13  1:45                                                 ` Steve Wise
2008-02-13  2:35                                                 ` Christoph Lameter
2008-02-13  3:25                                                   ` Jason Gunthorpe
2008-02-13  3:56                                                     ` Patrick Geoffray
2008-02-13  4:26                                                       ` Jason Gunthorpe
2008-02-13  4:47                                                         ` Patrick Geoffray
2008-02-13 18:51                                                     ` Christoph Lameter
2008-02-13 19:51                                                       ` Jason Gunthorpe
2008-02-13 20:36                                                         ` Christoph Lameter
2008-02-13  4:09                                                   ` Christian Bell
2008-02-13 19:00                                                     ` Christoph Lameter
2008-02-13 19:46                                                       ` Christian Bell
2008-02-13 20:32                                                         ` Christoph Lameter [this message]
2008-02-13 22:44                                                           ` Kanoj Sarcar
2008-02-13 23:02                                                             ` Christoph Lameter
2008-02-13 23:43                                                               ` Kanoj Sarcar
2008-02-13 23:48                                                                 ` Jesse Barnes
2008-02-14  0:56                                                                 ` [ofa-general] " Andrea Arcangeli
2008-02-14 19:35                                                                 ` Christoph Lameter
2008-02-13 23:23                                                     ` Pete Wyckoff
2008-02-14  0:01                                                       ` Jason Gunthorpe
2008-02-27 22:11                                                         ` Christoph Lameter
2008-02-13  1:55                                               ` Christian Bell
2008-02-13  2:19                                                 ` Christoph Lameter
2008-02-13  0:56                                           ` Christoph Lameter
2008-02-13 12:11                                           ` Christoph Raisch
2008-02-13 19:02                                             ` Christoph Lameter
2008-02-09  0:12               ` [patch 0/6] MMU Notifiers V6 Andrew Morton
2008-02-09  0:18                 ` Christoph Lameter
2008-02-13 14:31 ` Jack Steiner

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