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From: Mel Gorman <mgorman@techsingularity.net>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Linux-MM <linux-mm@kvack.org>, Rik van Riel <riel@surriel.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Li Zefan <lizefan@huawei.com>,
	cgroups@vger.kernel.org
Subject: Re: [PATCH 02/27] mm, vmscan: Check if cpusets are enabled during direct reclaim
Date: Wed, 9 Mar 2016 11:59:38 +0000	[thread overview]
Message-ID: <20160309115909.GA31585@techsingularity.net> (raw)
In-Reply-To: <56D8209C.5020103@suse.cz>

On Thu, Mar 03, 2016 at 12:31:40PM +0100, Vlastimil Babka wrote:
> On 02/23/2016 04:04 PM, Mel Gorman wrote:
> > Direct reclaim obeys cpusets but misses the cpusets_enabled() check.
> > The overhead is unlikely to be measurable in the direct reclaim
> > path which is expensive but there is no harm is doing it.
> > 
> > Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> > ---
> >  mm/vmscan.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 86eb21491867..de8d6226e026 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -2566,7 +2566,7 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
> >  		 * to global LRU.
> >  		 */
> >  		if (global_reclaim(sc)) {
> > -			if (!cpuset_zone_allowed(zone,
> > +			if (cpusets_enabled() && !cpuset_zone_allowed(zone,
> >  						 GFP_KERNEL | __GFP_HARDWALL))
> >  				continue;
> 
> Hmm, wouldn't it be nicer if cpuset_zone_allowed() itself did the right
> thing, and not each caller?
> 
> How about the patch below? (+CC)
> 

The patch appears to be layer upon the entire series but that in itself
is ok. This part is a problem

> An important function for cpusets is cpuset_node_allowed(), which acknowledges
> that if there's a single root CPU set, it must be trivially allowed. But the
> check "nr_cpusets() <= 1" doesn't use the cpusets_enabled_key static key in a
> proper way where static keys can reduce the overhead.


There is one check for the static key and a second for the count to see
if it's likely a valid cpuset that matters has been configured. The
point of that check was that it was lighter than __cpuset_zone_allowed
in the case where no cpuset is configured.

The patches are not equivalent.

-- 
Mel Gorman
SUSE Labs

  reply	other threads:[~2016-03-09 11:59 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-23 15:04 [RFC PATCH 00/27] Move LRU page reclaim from zones to nodes v2 Mel Gorman
2016-02-23 15:04 ` [PATCH 01/27] mm, page_alloc: Use ac->classzone_idx instead of zone_idx(preferred_zone) Mel Gorman
2016-02-23 18:04   ` Johannes Weiner
2016-03-03 10:37   ` Vlastimil Babka
2016-02-23 15:04 ` [PATCH 02/27] mm, vmscan: Check if cpusets are enabled during direct reclaim Mel Gorman
2016-02-23 18:06   ` Johannes Weiner
2016-03-03 11:31   ` Vlastimil Babka
2016-03-09 11:59     ` Mel Gorman [this message]
2016-03-09 12:30       ` Vlastimil Babka
2016-02-23 15:04 ` [PATCH 03/27] mm, vmstat: Add infrastructure for per-node vmstats Mel Gorman
2016-02-23 18:13   ` Johannes Weiner
2016-02-24  9:19     ` Mel Gorman
2016-02-23 15:04 ` [PATCH 04/27] mm, vmscan: Move lru_lock to the node Mel Gorman
2016-02-23 18:40   ` Johannes Weiner
2016-02-23 15:04 ` [PATCH 05/27] mm, vmscan: Move LRU lists to node Mel Gorman
2016-02-23 18:42   ` Johannes Weiner
2016-02-23 15:04 ` [PATCH 06/27] mm, vmscan: Begin reclaiming pages on a per-node basis Mel Gorman
2016-02-23 18:57   ` Johannes Weiner
2016-02-23 19:03     ` Johannes Weiner
2016-02-24 10:21     ` Mel Gorman
2016-02-23 15:04 ` [PATCH 07/27] mm, vmscan: Have kswapd only scan based on the highest requested zone Mel Gorman
2016-02-25 22:17   ` Johannes Weiner
2016-02-23 15:04 ` [PATCH 08/27] mm, vmscan: Make kswapd reclaim in terms of nodes Mel Gorman
2016-02-28 16:16   ` Johannes Weiner
2016-03-03 13:46   ` Vlastimil Babka
2016-03-09 14:45     ` Mel Gorman
2016-02-23 15:04 ` [PATCH 09/27] mm, vmscan: Simplify the logic deciding whether kswapd sleeps Mel Gorman
2016-02-28 16:16   ` Johannes Weiner
2016-02-23 15:04 ` [PATCH 10/27] mm, vmscan: By default have direct reclaim only shrink once per node Mel Gorman
2016-02-28 16:17   ` Johannes Weiner
2016-02-23 15:04 ` [PATCH 11/27] mm, vmscan: Clear congestion, dirty and need for compaction on a per-node basis Mel Gorman
2016-02-23 15:04 ` [PATCH 12/27] mm: vmscan: Do not reclaim from kswapd if there is any eligible zone Mel Gorman
2016-02-23 15:04 ` [PATCH 13/27] mm, vmscan: Make shrink_node decisions more node-centric Mel Gorman
2016-02-23 15:04 ` [PATCH 14/27] mm, memcg: Move memcg limit enforcement from zones to nodes Mel Gorman
2016-02-23 15:04 ` [PATCH 15/27] mm, workingset: Make working set detection node-aware Mel Gorman
2016-02-28 16:17   ` Johannes Weiner
2016-02-23 15:17 ` [PATCH 16/27] mm, page_alloc: Consider dirtyable memory in terms of nodes Mel Gorman
2016-02-28 16:17   ` Johannes Weiner
2016-02-23 15:18 ` [PATCH 17/27] mm: Move page mapped accounting to the node Mel Gorman
2016-02-23 15:18 ` [PATCH 18/27] mm: Rename NR_ANON_PAGES to NR_ANON_MAPPED Mel Gorman
2016-02-23 15:18 ` [PATCH 19/27] mm: Move most file-based accounting to the node Mel Gorman
2016-02-23 15:19 ` [PATCH 20/27] mm: Move vmscan writes and file write " Mel Gorman
2016-02-23 15:19 ` [PATCH 21/27] mm, vmscan: Update classzone_idx if buffer_heads_over_limit Mel Gorman
2016-02-23 15:19 ` [PATCH 22/27] mm, vmscan: Only wakeup kswapd once per node for the requested classzone Mel Gorman
2016-02-23 15:20 ` [PATCH 23/27] mm, vmscan: Account in vmstat for pages skipped during reclaim Mel Gorman
2016-02-23 15:20 ` [PATCH 24/27] mm: Convert zone_reclaim to node_reclaim Mel Gorman
2016-02-23 15:20 ` [PATCH 25/27] mm, vmscan: Add classzone information to tracepoints Mel Gorman
2016-02-23 15:21 ` [PATCH 26/27] mm, page_alloc: Remove fair zone allocation policy Mel Gorman
2016-02-23 15:21 ` [PATCH 27/27] mm: page_alloc: Cache the last node whose dirty limit is reached Mel Gorman
2016-02-23 17:15 ` [RFC PATCH 00/27] Move LRU page reclaim from zones to nodes v2 Christoph Lameter
2016-02-23 20:04 ` Johannes Weiner
2016-02-23 20:19   ` Mel Gorman
2016-02-23 20:59     ` Johannes Weiner
2016-02-23 21:58       ` Mel Gorman
2016-02-24  0:12         ` Johannes Weiner
2016-02-24 10:46           ` Mel Gorman
  -- strict thread matches above, loose matches on Subject: below --
2016-02-23 13:44 Mel Gorman
2016-02-23 13:44 ` [PATCH 02/27] mm, vmscan: Check if cpusets are enabled during direct reclaim Mel Gorman

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