From: Andrew Morton <akpm@linux-foundation.org>
To: Mel Gorman <mgorman@suse.de>
Cc: 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>
Subject: Re: [PATCH 00/14] Swap-over-NBD without deadlocking v5
Date: Wed, 6 Jul 2011 16:51:46 -0700 [thread overview]
Message-ID: <20110706165146.be7ab61b.akpm@linux-foundation.org> (raw)
In-Reply-To: <1308575540-25219-1-git-send-email-mgorman@suse.de>
On Mon, 20 Jun 2011 14:12:06 +0100
Mel Gorman <mgorman@suse.de> wrote:
> Swapping over NBD is something that is technically possible but not
> often advised. While there are number of guides on the internet
> on how to configure it and nbd-client supports a -swap switch to
> "prevent deadlocks", the fact of the matter is a machine using NBD
> for swap can be locked up within minutes if swap is used intensively.
>
> The problem is that network block devices do not use mempools like
> normal block devices do. As the host cannot control where they receive
> packets from, they cannot reliably work out in advance how much memory
> they might need.
>
> Some years ago, Peter Ziljstra developed a series of patches that
> supported swap over an NFS that some distributions are carrying in
> their kernels. This patch series borrows very heavily from Peter's work
> to support swapping over NBD (the relatively straight-forward case)
> and uses throttling instead of dynamically resized memory reserves
> so the series is not too unwieldy for review.
I have to say, I look over these patches and my mind wants to turn to
things like puppies. And ice cream.
There's quite some complexity added here in areas which are already
reliably unreliable and afaik swap-over-NBD is not a thing which a lot
of people want to do. I can see that swap-over-NFS would be useful to
some people, and the fact that distros are carrying swap-over-NFS
patches has weight.
Do these patches lead on to swap-over-NFS? If so, how much more
additional complexity are we buying into for that?
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next prev parent reply other threads:[~2011-07-06 23:52 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-20 13:12 [PATCH 00/14] Swap-over-NBD without deadlocking v5 Mel Gorman
2011-06-20 13:12 ` [PATCH 01/14] mm: Serialize access to min_free_kbytes Mel Gorman
2011-07-06 23:44 ` Andrew Morton
2011-07-07 9:17 ` Mel Gorman
2011-06-20 13:12 ` [PATCH 02/14] mm: sl[au]b: Add knowledge of PFMEMALLOC reserve pages Mel Gorman
2011-06-20 13:12 ` [PATCH 03/14] mm: Introduce __GFP_MEMALLOC to allow access to emergency reserves Mel Gorman
2011-06-20 13:12 ` [PATCH 04/14] mm: allow PF_MEMALLOC from softirq context Mel Gorman
2011-06-20 13:12 ` [PATCH 05/14] mm: Ignore mempolicies when using ALLOC_NO_WATERMARK Mel Gorman
2011-06-20 13:12 ` [PATCH 06/14] net: Introduce sk_allocation() to allow addition of GFP flags depending on the individual socket Mel Gorman
2011-06-20 13:12 ` [PATCH 07/14] netvm: Allow the use of __GFP_MEMALLOC by specific sockets Mel Gorman
2011-06-20 13:12 ` [PATCH 08/14] netvm: Allow skb allocation to use PFMEMALLOC reserves Mel Gorman
2011-06-20 13:12 ` [PATCH 09/14] netvm: Propagate page->pfmemalloc to skb Mel Gorman
2011-06-20 13:12 ` [PATCH 10/14] netvm: Set PF_MEMALLOC as appropriate during SKB processing Mel Gorman
2011-06-20 13:12 ` [PATCH 11/14] mm: Micro-optimise slab to avoid a function call Mel Gorman
2011-06-20 13:12 ` [PATCH 12/14] nbd: Set SOCK_MEMALLOC for access to PFMEMALLOC reserves Mel Gorman
2011-06-20 13:12 ` [PATCH 13/14] mm: Throttle direct reclaimers if PF_MEMALLOC reserves are low and swap is backed by network storage Mel Gorman
2011-06-20 13:12 ` [PATCH 14/14] mm: Account for the number of times direct reclaimers get throttled Mel Gorman
2011-07-06 23:51 ` Andrew Morton [this message]
2011-07-07 9:47 ` [PATCH 00/14] Swap-over-NBD without deadlocking v5 Mel Gorman
2011-07-07 12:58 ` Christoph Hellwig
2011-07-15 14:10 ` Mel Gorman
2011-07-15 15:27 ` Christoph Hellwig
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