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>,
Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH 7/9] mm, page_alloc: remove stop_machine from build_all_zonelists
Date: Fri, 14 Jul 2017 10:59:32 +0100 [thread overview]
Message-ID: <20170714095932.jihl6h3y77hxyyiu@suse.de> (raw)
In-Reply-To: <20170714080006.7250-8-mhocko@kernel.org>
On Fri, Jul 14, 2017 at 10:00:04AM +0200, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
>
> build_all_zonelists has been (ab)using stop_machine to make sure that
> zonelists do not change while somebody is looking at them. This is
> is just a gross hack because a) it complicates the context from which
> we can call build_all_zonelists (see 3f906ba23689 ("mm/memory-hotplug:
> switch locking to a percpu rwsem")) and b) is is not really necessary
> especially after "mm, page_alloc: simplify zonelist initialization".
>
> Updates of the zonelists happen very seldom, basically only when a zone
> becomes populated during memory online or when it loses all the memory
> during offline. A racing iteration over zonelists could either miss a
> zone or try to work on one zone twice. Both of these are something we
> can live with occasionally because there will always be at least one
> zone visible so we are not likely to fail allocation too easily for
> example.
>
> Signed-off-by: Michal Hocko <mhocko@suse.com>
This patch is contingent on the last patch which updates in place
instead of zeroing the early part of the zonelist first but needs to fix
the stack usage issues. I think it's also worth pointing out in the
changelog that stop_machine never gave the guarantees it claimed as a
process iterating through the zonelist can be stopped so when it resumes
the zonelist has changed underneath it. Doing it online is roughly
equivalent in terms of safety.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2017-07-14 9:59 UTC|newest]
Thread overview: 54+ 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
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 [this message]
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 7/9] mm, page_alloc: remove stop_machine from build_all_zonelists Michal Hocko
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