Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
From: Michal Hocko <mhocko@kernel.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	Mel Gorman <mgorman@suse.de>,
	Johannes Weiner <hannes@cmpxchg.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 6/9] mm, page_alloc: simplify zonelist initialization
Date: Thu, 20 Jul 2017 09:19:35 +0200
Message-ID: <20170720071935.GC9058@dhcp22.suse.cz> (raw)
In-Reply-To: <d23a3570-e39c-d708-c9d1-80258d45a97f@suse.cz>

On Thu 20-07-17 08:55:42, Vlastimil Babka wrote:
> On 07/14/2017 10:00 AM, Michal Hocko wrote:
> > From: Michal Hocko <mhocko@suse.com>
> > 
> > build_zonelists gradually builds zonelists from the nearest to the most
> > distant node. As we do not know how many populated zones we will have in
> > each node we rely on the _zoneref to terminate initialized part of the
> > zonelist by a NULL zone. While this is functionally correct it is quite
> > suboptimal because we cannot allow updaters to race with zonelists
> > users because they could see an empty zonelist and fail the allocation
> > or hit the OOM killer in the worst case.
> > 
> > We can do much better, though. We can store the node ordering into an
> > already existing node_order array and then give this array to
> > build_zonelists_in_node_order and do the whole initialization at once.
> > zonelists consumers still might see halfway initialized state but that
> > should be much more tolerateable because the list will not be empty and
> > they would either see some zone twice or skip over some zone(s) in the
> > worst case which shouldn't lead to immediate failures.
> > 
> > This patch alone doesn't introduce any functional change yet, though, it
> > is merely a preparatory work for later changes.
> > 
> > Signed-off-by: Michal Hocko <mhocko@suse.com>
> 
> I've collected the fold-ups from this thread and looked at the result as
> single patch. Sems OK, just two things:
> - please rename variable "i" in build_zonelists() to e.g. "nr_nodes"
> - the !CONFIG_NUMA variant of build_zonelists() won't build, because it
> doesn't declare nr_zones variable

Thanks! I will fold this in.
---
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c0d3e8eeb150..6f192405e469 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4957,7 +4957,7 @@ static void build_thisnode_zonelists(pg_data_t *pgdat)
 static void build_zonelists(pg_data_t *pgdat)
 {
 	static int node_order[MAX_NUMNODES];
-	int node, load, i = 0;
+	int node, load, nr_nodes = 0;
 	nodemask_t used_mask;
 	int local_node, prev_node;
 
@@ -4978,12 +4978,12 @@ static void build_zonelists(pg_data_t *pgdat)
 		    node_distance(local_node, prev_node))
 			node_load[node] = load;
 
-		node_order[i++] = node;
+		node_order[nr_nodes++] = node;
 		prev_node = node;
 		load--;
 	}
 
-	build_zonelists_in_node_order(pgdat, node_order, i);
+	build_zonelists_in_node_order(pgdat, node_order, nr_nodes);
 	build_thisnode_zonelists(pgdat);
 }
 
@@ -5013,10 +5013,11 @@ static void build_zonelists(pg_data_t *pgdat)
 {
 	int node, local_node;
 	struct zoneref *zonerefs;
+	int nr_zones;
 
 	local_node = pgdat->node_id;
 
-	zonrefs = pgdat->node_zonelists[ZONELIST_FALLBACK]._zonerefs;
+	zonerefs = pgdat->node_zonelists[ZONELIST_FALLBACK]._zonerefs;
 	nr_zones = build_zonerefs_node(pgdat, zonerefs);
 	zonerefs += nr_zones;
 

-- 
Michal Hocko
SUSE Labs

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

  reply index

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-07-14  7:59 [PATCH 0/9] cleanup zonelists initialization Michal Hocko
2017-07-14  7:59 ` [PATCH 1/9] mm, page_alloc: rip out ZONELIST_ORDER_ZONE Michal Hocko
2017-07-14  9:36   ` Mel Gorman
2017-07-14 10:47     ` Michal Hocko
2017-07-14 11:16       ` Mel Gorman
2017-07-14 11:38         ` Michal Hocko
2017-07-14 12:56           ` Mel Gorman
2017-07-14 13:01             ` Mel Gorman
2017-07-14 13:08             ` Michal Hocko
2017-07-19  9:33   ` Vlastimil Babka
2017-07-19 13:44     ` Michal Hocko
2017-07-14  7:59 ` [PATCH 2/9] mm, page_alloc: remove boot pageset initialization from memory hotplug Michal Hocko
2017-07-14  9:39   ` Mel Gorman
2017-07-19 13:15   ` Vlastimil Babka
2017-07-14  8:00 ` [PATCH 3/9] mm, page_alloc: do not set_cpu_numa_mem on empty nodes initialization Michal Hocko
2017-07-14  9:48   ` Mel Gorman
2017-07-14 10:50     ` Michal Hocko
2017-07-14 12:32       ` Mel Gorman
2017-07-14 12:39         ` Michal Hocko
2017-07-14 12:56           ` Mel Gorman
2017-07-19 13:19   ` Vlastimil Babka
2017-07-14  8:00 ` [PATCH 4/9] mm, memory_hotplug: drop zone from build_all_zonelists Michal Hocko
2017-07-19 13:33   ` Vlastimil Babka
2017-07-20  8:15     ` Michal Hocko
2017-07-14  8:00 ` [PATCH 5/9] mm, memory_hotplug: remove explicit build_all_zonelists from try_online_node Michal Hocko
2017-07-14 12:14   ` Michal Hocko
2017-07-20  6:13   ` Vlastimil Babka
2017-07-14  8:00 ` [PATCH 6/9] mm, page_alloc: simplify zonelist initialization Michal Hocko
2017-07-14  9:55   ` Mel Gorman
2017-07-14 10:51     ` Michal Hocko
2017-07-14 12:46   ` Mel Gorman
2017-07-14 13:02     ` Michal Hocko
2017-07-14 14:18       ` Mel Gorman
2017-07-17  6:06         ` Michal Hocko
2017-07-17  8:07           ` Mel Gorman
2017-07-17  8:19             ` Michal Hocko
2017-07-17  8:58               ` Mel Gorman
2017-07-17  9:15                 ` Michal Hocko
2017-07-20  6:55   ` Vlastimil Babka
2017-07-20  7:19     ` Michal Hocko [this message]
2017-07-14  8:00 ` [PATCH 7/9] mm, page_alloc: remove stop_machine from build_all_zonelists Michal Hocko
2017-07-14  9:59   ` Mel Gorman
2017-07-14 11:00     ` Michal Hocko
2017-07-14 12:47       ` Mel Gorman
2017-07-14 11:29   ` Vlastimil Babka
2017-07-14 11:43     ` Michal Hocko
2017-07-14 11:45       ` Michal Hocko
2017-07-20  6:16         ` Vlastimil Babka
2017-07-20  7:24   ` Vlastimil Babka
2017-07-20  9:21     ` Michal Hocko
2017-07-14  8:00 ` [PATCH 8/9] mm, memory_hotplug: get rid of zonelists_mutex Michal Hocko
2017-07-14  8:00 ` [PATCH 9/9] mm, sparse, page_ext: drop ugly N_HIGH_MEMORY branches for allocations Michal Hocko
2017-07-20  8:04   ` Vlastimil Babka
2017-07-21 14:39 [PATCH -v1 0/9] cleanup zonelists initialization Michal Hocko
2017-07-21 14:39 ` [PATCH 6/9] mm, page_alloc: simplify zonelist initialization Michal Hocko
2017-07-24  9:25   ` Vlastimil Babka

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20170720071935.GC9058@dhcp22.suse.cz \
    --to=mhocko@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=hannes@cmpxchg.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mgorman@suse.de \
    --cc=vbabka@suse.cz \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-mm Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mm/0 linux-mm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mm linux-mm/ https://lore.kernel.org/linux-mm \
		linux-mm@kvack.org
	public-inbox-index linux-mm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kvack.linux-mm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git