From: Mel Gorman <mgorman@suse.de>
To: Christoph Lameter <cl@linux.com>
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: Mon, 13 Feb 2012 10:12:39 +0000 [thread overview]
Message-ID: <20120213101239.GU5938@suse.de> (raw)
In-Reply-To: <alpine.DEB.2.00.1202101606530.3840@router.home>
On Fri, Feb 10, 2012 at 04:07:57PM -0600, Christoph Lameter wrote:
> Proposal for a patch for slub to move the pfmemalloc handling out of the
> fastpath by simply not assigning a per cpu slab when pfmemalloc processing
> is going on.
>
>
>
> Subject: [slub] Fix so that no mods are required for the fast path
>
> Remove the check for pfmemalloc from the alloc hotpath and put the logic after
> the election of a new per cpu slab.
>
> For a pfmemalloc page do not use the fast path but force use of the slow
> path (which is also used for the debug case).
>
> Signed-off-by: Christoph Lameter <cl@linux.com>
>
This weakens pfmemalloc processing in the following way
1. Process that is performance network swap calls __slab_alloc.
pfmemalloc_match is true so the freelist is loaded and
c->freelist is now pointing to a pfmemalloc page
2. Process that is attempting normal allocations calls slab_alloc,
finds the pfmemalloc page on the freelist and uses it because it
did not check pfmemalloc_match()
The patch allows non-pfmemalloc allocations to use pfmemalloc pages with
the kmalloc slabs being the most vunerable caches on the grounds they are
most likely to have a mix of pfmemalloc and !pfmemalloc requests. Patch
14 will still protect the system as processes will get throttled if the
pfmemalloc reserves get depleted so performance will not degrade as smoothly.
Assuming this passes testing, I'll add the patch to the series with the
information above included in the changelog.
Thanks Christoph.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2012-02-13 10:12 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
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 [this message]
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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