From: Christoph Lameter <cl@linux.com>
To: Mel Gorman <mgorman@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linux-MM <linux-mm@kvack.org>,
Linux-Netdev <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
David Miller <davem@davemloft.net>, Neil Brown <neilb@suse.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Pekka Enberg <penberg@cs.helsinki.fi>
Subject: Re: [PATCH 02/15] mm: sl[au]b: Add knowledge of PFMEMALLOC reserve pages
Date: Thu, 9 Feb 2012 13:53:58 -0600 (CST) [thread overview]
Message-ID: <alpine.DEB.2.00.1202091345540.4413@router.home> (raw)
In-Reply-To: <20120209125018.GN5938@suse.de>
On Thu, 9 Feb 2012, Mel Gorman wrote:
> Ok, I am working on a solution that does not affect any of the existing
> slab structures. Between that and the fact we check if there are any
> memalloc_socks after patch 12, the impact for normal systems is an additional
> branch in ac_get_obj() and ac_put_obj()
That sounds good in particular since some other things came up again,
sigh. Have not had time to see if an alternate approach works.
> > We have been down this road too many times. Logic is added to critical
> > paths and memory structures grow. This is not free. And for NBD swap
> > support? Pretty exotic use case.
> >
>
> NFS support is the real target. NBD is the logical starting point and
> NFS needs the same support.
But this is already a pretty strange use case on multiple levels. Swap is
really detrimental to performance. Its a kind of emergency outlet that
gets worse with every new step that increases the differential in
performance between disk and memory. On top of that you want to add
special code in various subsystems to also do that over the network.
Sigh. I think we agreed a while back that we want to limit the amount of
I/O triggered from reclaim paths? AFAICT many filesystems do not support
writeout from reclaim anymore because of all the issues that arise at that
level.
We have numerous other mechanisms that can compress swap etc and provide
ways to work around the problem without I/O which has always be
troublesome and these fixes are likely only to work in a very limited
way causing a lot of maintenance effort because (given the exotic
nature) it is highly likely that there are cornercases that only will be
triggered in rare cases.
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next prev parent reply other threads:[~2012-02-09 19:54 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-06 22:56 [PATCH 00/15] Swap-over-NBD without deadlocking V8 Mel Gorman
2012-02-06 22:56 ` [PATCH 01/15] mm: Serialize access to min_free_kbytes Mel Gorman
2012-02-08 18:47 ` Rik van Riel
2012-02-06 22:56 ` [PATCH 02/15] mm: sl[au]b: Add knowledge of PFMEMALLOC reserve pages Mel Gorman
2012-02-07 16:27 ` Christoph Lameter
2012-02-08 14:45 ` Mel Gorman
2012-02-08 15:14 ` Christoph Lameter
2012-02-08 16:34 ` Mel Gorman
2012-02-08 19:49 ` Christoph Lameter
2012-02-08 21:23 ` Mel Gorman
2012-02-08 22:13 ` Christoph Lameter
2012-02-09 12:50 ` Mel Gorman
2012-02-09 19:53 ` Christoph Lameter [this message]
2012-02-10 10:26 ` Mel Gorman
2012-02-10 21:01 ` Christoph Lameter
2012-02-10 22:07 ` Christoph Lameter
2012-02-13 10:12 ` Mel Gorman
2012-02-13 11:10 ` Mel Gorman
2012-02-06 22:56 ` [PATCH 03/15] mm: Introduce __GFP_MEMALLOC to allow access to emergency reserves Mel Gorman
2012-02-06 22:56 ` [PATCH 04/15] mm: allow PF_MEMALLOC from softirq context Mel Gorman
2012-02-06 22:56 ` [PATCH 05/15] mm: Ignore mempolicies when using ALLOC_NO_WATERMARK Mel Gorman
2012-02-06 22:56 ` [PATCH 06/15] net: Introduce sk_allocation() to allow addition of GFP flags depending on the individual socket Mel Gorman
2012-02-06 22:56 ` [PATCH 07/15] netvm: Allow the use of __GFP_MEMALLOC by specific sockets Mel Gorman
2012-02-06 22:56 ` [PATCH 08/15] netvm: Allow skb allocation to use PFMEMALLOC reserves Mel Gorman
2012-02-06 22:56 ` [PATCH 09/15] netvm: Propagate page->pfmemalloc to skb Mel Gorman
2012-02-06 22:56 ` [PATCH 10/15] netvm: Propagate page->pfmemalloc from netdev_alloc_page " Mel Gorman
2012-02-07 23:38 ` Alexander Duyck
2012-02-08 15:23 ` Mel Gorman
2012-02-06 22:56 ` [PATCH 11/15] netvm: Set PF_MEMALLOC as appropriate during SKB processing Mel Gorman
2012-02-06 22:56 ` [PATCH 12/15] mm: Micro-optimise slab to avoid a function call Mel Gorman
2012-02-06 22:56 ` [PATCH 13/15] nbd: Set SOCK_MEMALLOC for access to PFMEMALLOC reserves Mel Gorman
2012-02-06 22:56 ` [PATCH 14/15] mm: Throttle direct reclaimers if PF_MEMALLOC reserves are low and swap is backed by network storage Mel Gorman
2012-02-06 22:56 ` [PATCH 15/15] mm: Account for the number of times direct reclaimers get throttled Mel Gorman
2012-02-07 12:45 ` [PATCH 00/15] Swap-over-NBD without deadlocking V8 Hillf Danton
2012-02-07 13:27 ` Mel Gorman
2012-02-08 12:51 ` Hillf Danton
2012-02-08 15:26 ` Mel Gorman
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