From: Mel Gorman <mgorman@suse.de>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Vlastimil Babka <vbabka@suse.cz>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 6/9] mm, page_alloc: simplify zonelist initialization
Date: Fri, 14 Jul 2017 15:18:23 +0100 [thread overview]
Message-ID: <20170714141823.2j7t37t6zdzdf3sv@suse.de> (raw)
In-Reply-To: <20170714130242.GQ2618@dhcp22.suse.cz>
On Fri, Jul 14, 2017 at 03:02:42PM +0200, Michal Hocko wrote:
> > It *might* be safer given the next patch to zero out the remainder of
> > the _zonerefs to that there is no combination of node add/remove that has
> > an iterator working with a semi-valid _zoneref which is beyond the last
> > correct value. It *should* be safe as the very last entry will always
> > be null but if you don't zero it out, it is possible for iterators to be
> > working beyond the "end" of the zonelist for a short window.
>
> yes that is true but there will always be terminating NULL zone and I
> found that acceptable. It is basically the same thing as accessing an
> empty zone or a zone twice. Or do you think this is absolutely necessary
> to handle?
>
I don't think it's absolutely necessary. While you could construct some
odd behaviour for iterators currently past the end of the list, they would
eventually encounter a NULL.
> > Otherwise think it's ok including my stupid comment about node_order
> > stack usage.
>
> What do you think about this on top?
> ---
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 49bade7ff049..3b98524c04ec 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4913,20 +4913,21 @@ static int find_next_best_node(int node, nodemask_t *used_node_mask)
> * This results in maximum locality--normal zone overflows into local
> * DMA zone, if any--but risks exhausting DMA zone.
> */
> -static void build_zonelists_in_node_order(pg_data_t *pgdat, int *node_order)
> +static void build_zonelists_in_node_order(pg_data_t *pgdat, int *node_order,
> + unsigned nr_nodes)
> {
> struct zonelist *zonelist;
> - int i, zoneref_idx = 0;
> + int i, nr_zones = 0;
>
> zonelist = &pgdat->node_zonelists[ZONELIST_FALLBACK];
>
> - for (i = 0; i < MAX_NUMNODES; i++) {
> + for (i = 0; i < nr_nodes; i++) {
The first iteration is then -- for (i = 0; i < 0; i++)
Fairly sure that's not what you meant.
> pg_data_t *node = NODE_DATA(node_order[i]);
>
> - zoneref_idx = build_zonelists_node(node, zonelist, zoneref_idx);
> + nr_zones = build_zonelists_node(node, zonelist, nr_zones);
I meant converting build_zonelists_node and passing in &nr_zones and
returning false when an empty node is encountered. In this context,
it's also not about zones, it really is nr_zonerefs. Rename nr_zones in
build_zonelists_node as well.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2017-07-14 14:18 UTC|newest]
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 [this message]
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
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
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