From: Mel Gorman <mgorman@suse.de>
To: NeilBrown <neilb@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>,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH 02/13] mm: sl[au]b: Add knowledge of PFMEMALLOC reserve pages
Date: Tue, 26 Apr 2011 14:59:40 +0100 [thread overview]
Message-ID: <20110426135940.GE4658@suse.de> (raw)
In-Reply-To: <20110426213758.450f6f49@notabene.brown>
On Tue, Apr 26, 2011 at 09:37:58PM +1000, NeilBrown wrote:
> On Tue, 26 Apr 2011 08:36:43 +0100 Mel Gorman <mgorman@suse.de> wrote:
>
> > + /*
> > + * If there are full empty slabs and we were not forced to
> > + * allocate a slab, mark this one !pfmemalloc
> > + */
> > + l3 = cachep->nodelists[numa_mem_id()];
> > + if (!list_empty(&l3->slabs_free) && force_refill) {
> > + struct slab *slabp = virt_to_slab(objp);
> > + slabp->pfmemalloc = false;
> > + clear_obj_pfmemalloc(&objp);
> > + check_ac_pfmemalloc(cachep, ac);
> > + return objp;
> > + }
>
> The comment doesn't match the code. I think you need to remove the words
> "full" and "not" assuming the code is correct which it probably is...
>
I'll fix up the comment, you're right, it's confusing.
> But the code seems to be much more complex than Peter's original, and I don't
> see the gain.
>
You're right, it is more complex.
> Peter's code had only one 'reserved' flag for each kmem_cache.
The reserve was set in a per-cpu structure so there was a "lag" time
before that information was available to other CPUs. Fine on smaller
machines but a bit more of a problem today.
> You seem to
> have one for every slab. I don't see the point.
> It is true that yours is in some sense more fair - but I'm not sure the
> complexity is worth it.
>
More fairness was one of the objects.
> Was there some particular reason you made the change?
>
This version survives under considerably more stress than Peter's
original version did without requiring the additional complexity of
memory reserves.
--
Mel Gorman
SUSE Labs
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next prev parent reply other threads:[~2011-04-26 13:59 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-26 7:36 [PATCH 00/13] Swap-over-NBD without deadlocking Mel Gorman
2011-04-26 7:36 ` [PATCH 01/13] mm: Serialize access to min_free_kbytes Mel Gorman
2011-04-26 7:36 ` [PATCH 02/13] mm: sl[au]b: Add knowledge of PFMEMALLOC reserve pages Mel Gorman
2011-04-26 11:15 ` NeilBrown
2011-04-26 11:33 ` Mel Gorman
2011-04-26 12:05 ` NeilBrown
2011-04-26 11:37 ` NeilBrown
2011-04-26 13:59 ` Mel Gorman [this message]
2011-04-27 23:21 ` NeilBrown
2011-04-28 9:46 ` Mel Gorman
2011-04-26 7:36 ` [PATCH 03/13] mm: Introduce __GFP_MEMALLOC to allow access to emergency reserves Mel Gorman
2011-04-26 9:49 ` NeilBrown
2011-04-26 10:36 ` Mel Gorman
2011-04-26 10:53 ` NeilBrown
2011-04-26 14:00 ` Mel Gorman
2011-04-26 7:36 ` [PATCH 04/13] mm: allow PF_MEMALLOC from softirq context Mel Gorman
2011-04-26 7:36 ` [PATCH 05/13] mm: Ignore mempolicies when using ALLOC_NO_WATERMARK Mel Gorman
2011-04-26 7:36 ` [PATCH 06/13] net: Introduce sk_allocation() to allow addition of GFP flags depending on the individual socket Mel Gorman
2011-04-26 7:36 ` [PATCH 07/13] netvm: Allow the use of __GFP_MEMALLOC by specific sockets Mel Gorman
2011-04-26 7:36 ` [PATCH 08/13] netvm: Allow skb allocation to use PFMEMALLOC reserves Mel Gorman
2011-04-26 7:36 ` [PATCH 09/13] netvm: Set PF_MEMALLOC as appropriate during SKB processing Mel Gorman
2011-04-26 12:21 ` NeilBrown
2011-04-26 14:10 ` Mel Gorman
2011-04-26 23:22 ` NeilBrown
2011-04-26 7:36 ` [PATCH 10/13] mm: Micro-optimise slab to avoid a function call Mel Gorman
2011-04-26 7:36 ` [PATCH 11/13] nbd: Set SOCK_MEMALLOC for access to PFMEMALLOC reserves Mel Gorman
2011-04-26 7:36 ` [PATCH 12/13] mm: Throttle direct reclaimers if PF_MEMALLOC reserves are low and swap is backed by network storage Mel Gorman
2011-04-26 12:30 ` NeilBrown
2011-04-26 14:26 ` Mel Gorman
2011-04-26 23:18 ` NeilBrown
2011-04-27 8:36 ` Mel Gorman
2011-04-26 7:36 ` [PATCH 13/13] mm: Account for the number of times direct reclaimers get throttled Mel Gorman
2011-04-26 12:35 ` NeilBrown
2011-04-26 14:26 ` Mel Gorman
2011-04-26 14:23 ` [PATCH 00/13] Swap-over-NBD without deadlocking Peter Zijlstra
2011-04-26 14:46 ` Mel Gorman
2011-04-26 14:50 ` Peter Zijlstra
2011-04-27 8:43 ` Mel Gorman
2011-04-28 13:31 ` Pavel Machek
2011-04-28 13:42 ` Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2011-04-27 16:07 [PATCH 00/13] Swap-over-NBD without deadlocking v3 Mel Gorman
2011-04-27 16:08 ` [PATCH 02/13] mm: sl[au]b: Add knowledge of PFMEMALLOC reserve pages Mel Gorman
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