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From: Michal Hocko <mhocko@kernel.org>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Linux-MM <linux-mm@kvack.org>, Rik van Riel <riel@surriel.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Johannes Weiner <hannes@cmpxchg.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 15/27] mm, page_alloc: Consider dirtyable memory in terms of nodes
Date: Wed, 22 Jun 2016 16:27:57 +0200	[thread overview]
Message-ID: <20160622142756.GH9208@dhcp22.suse.cz> (raw)
In-Reply-To: <20160622141521.GC7527@dhcp22.suse.cz>

On Wed 22-06-16 16:15:21, Michal Hocko wrote:
> On Tue 21-06-16 15:15:54, Mel Gorman wrote:
> > Historically dirty pages were spread among zones but now that LRUs are
> > per-node it is more appropriate to consider dirty pages in a node.
> 
> I think this should deserve a note that a behavior for 32b highmem
> systems will change and could lead to early write throttling and
> observable stalls as a result because highmem_dirtyable_memory will
> always return totalhigh_pages regardless of how much is free resp. on
> LRUs so we can overestimate it.
> 
> Highmem is usually used for LRU pages but there are other allocations
> which can use it (e.g. vmalloc). I understand how this is both an
> inherent problem of 32b with a larger high:low ratio and why it is hard
> to at least pretend we can cope with it with node based approach but we
> should at least document it.
> 
> I workaround would be to enable highmem_dirtyable_memory which can lead
> to premature OOM killer for some workloads AFAIR.
[...]
> >  static unsigned long highmem_dirtyable_memory(unsigned long total)
> >  {
> >  #ifdef CONFIG_HIGHMEM
> > -	int node;
> >  	unsigned long x = 0;
> > -	int i;
> > -
> > -	for_each_node_state(node, N_HIGH_MEMORY) {
> > -		for (i = 0; i < MAX_NR_ZONES; i++) {
> > -			struct zone *z = &NODE_DATA(node)->node_zones[i];
> >  
> > -			if (is_highmem(z))
> > -				x += zone_dirtyable_memory(z);
> > -		}
> > -	}

Hmm, I have just noticed that we have NR_ZONE_LRU_ANON resp.
NR_ZONE_LRU_FILE so we can estimate the amount of highmem contribution
to the global counters by the following or similar:

	for_each_node_state(node, N_HIGH_MEMORY) {
		for (i = 0; i < MAX_NR_ZONES; i++) {
			struct zone *z = &NODE_DATA(node)->node_zones[i];

			if (!is_highmem(z))
				continue;

			x += zone_page_state(z, NR_FREE_PAGES) + zone_page_state(z, NR_ZONE_LRU_FILE) - high_wmark_pages(zone);
		}

high wmark reduction would be to emulate the reserve. What do you think?
-- 
Michal Hocko
SUSE Labs

  reply	other threads:[~2016-06-22 14:28 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-21 14:15 [PATCH 00/27] Move LRU page reclaim from zones to nodes v7 Mel Gorman
2016-06-21 14:15 ` [PATCH 01/27] mm, vmstat: Add infrastructure for per-node vmstats Mel Gorman
2016-06-21 14:15 ` [PATCH 02/27] mm, vmscan: Move lru_lock to the node Mel Gorman
2016-06-21 14:15 ` [PATCH 03/27] mm, vmscan: Move LRU lists to node Mel Gorman
2016-06-22 12:50   ` Vlastimil Babka
2016-06-21 14:15 ` [PATCH 04/27] mm, vmscan: Begin reclaiming pages on a per-node basis Mel Gorman
2016-06-22 14:04   ` Vlastimil Babka
2016-06-22 16:00     ` Vlastimil Babka
2016-06-23 11:07       ` Mel Gorman
2016-06-23 11:13         ` Michal Hocko
2016-06-23 10:58     ` Mel Gorman
2016-06-21 14:15 ` [PATCH 05/27] mm, vmscan: Have kswapd only scan based on the highest requested zone Mel Gorman
2016-06-21 14:15 ` [PATCH 06/27] mm, vmscan: Make kswapd reclaim in terms of nodes Mel Gorman
2016-06-21 14:15 ` [PATCH 07/27] mm, vmscan: Remove balance gap Mel Gorman
2016-06-21 14:15 ` [PATCH 08/27] mm, vmscan: Simplify the logic deciding whether kswapd sleeps Mel Gorman
2016-06-22 15:30   ` Vlastimil Babka
2016-06-21 14:15 ` [PATCH 09/27] mm, vmscan: By default have direct reclaim only shrink once per node Mel Gorman
2016-06-21 14:15 ` [PATCH 10/27] mm, vmscan: Remove duplicate logic clearing node congestion and dirty state Mel Gorman
2016-06-21 14:15 ` [PATCH 11/27] mm: vmscan: Do not reclaim from kswapd if there is any eligible zone Mel Gorman
2016-06-21 14:15 ` [PATCH 12/27] mm, vmscan: Make shrink_node decisions more node-centric Mel Gorman
2016-06-22 13:20   ` Michal Hocko
2016-06-22 15:42   ` Vlastimil Babka
2016-06-21 14:15 ` [PATCH 13/27] mm, memcg: Move memcg limit enforcement from zones to nodes Mel Gorman
2016-06-22 13:15   ` Michal Hocko
2016-06-21 14:15 ` [PATCH 14/27] mm, workingset: Make working set detection node-aware Mel Gorman
2016-06-21 14:15 ` [PATCH 15/27] mm, page_alloc: Consider dirtyable memory in terms of nodes Mel Gorman
2016-06-22 14:15   ` Michal Hocko
2016-06-22 14:27     ` Michal Hocko [this message]
2016-06-23 12:53       ` Mel Gorman
2016-06-23 13:13         ` Michal Hocko
2016-06-21 14:15 ` [PATCH 16/27] mm: Move page mapped accounting to the node Mel Gorman
2016-06-21 22:32   ` Andrew Morton
2016-06-23  8:35     ` Mel Gorman
2016-06-22 14:35   ` Michal Hocko
2016-06-21 14:15 ` [PATCH 17/27] mm: Rename NR_ANON_PAGES to NR_ANON_MAPPED Mel Gorman
2016-06-22 14:28   ` Michal Hocko
2016-06-21 14:15 ` [PATCH 18/27] mm: Move most file-based accounting to the node Mel Gorman
2016-06-22 14:38   ` Michal Hocko
2016-06-21 14:15 ` [PATCH 19/27] mm: Move vmscan writes and file write " Mel Gorman
2016-06-22 14:40   ` Michal Hocko
2016-06-23 13:57     ` Mel Gorman
2016-06-23 14:06       ` Vlastimil Babka
2016-06-23 16:03         ` Mel Gorman
2016-06-21 14:15 ` [PATCH 20/27] mm, vmscan: Update classzone_idx if buffer_heads_over_limit Mel Gorman
2016-06-22 14:49   ` Michal Hocko
2016-06-21 14:16 ` [PATCH 21/27] mm, vmscan: Only wakeup kswapd once per node for the requested classzone Mel Gorman
2016-06-22 16:08   ` Vlastimil Babka
2016-06-21 14:16 ` [PATCH 22/27] mm: Convert zone_reclaim to node_reclaim Mel Gorman
2016-06-21 14:16 ` [PATCH 23/27] mm, vmscan: Add classzone information to tracepoints Mel Gorman
2016-06-21 14:16 ` [PATCH 24/27] mm, page_alloc: Remove fair zone allocation policy Mel Gorman
2016-06-21 14:16 ` [PATCH 25/27] mm: page_alloc: Cache the last node whose dirty limit is reached Mel Gorman
2016-06-21 14:16 ` [PATCH 26/27] mm: vmstat: Replace __count_zone_vm_events with a zone id equivalent Mel Gorman
2016-06-21 14:16 ` [PATCH 27/27] mm: vmstat: Account per-zone stalls and pages skipped during reclaim Mel Gorman
2016-06-23 10:26 ` [PATCH 00/27] Move LRU page reclaim from zones to nodes v7 Mel Gorman
2016-06-23 11:27   ` Michal Hocko
2016-06-23 12:33     ` Mel Gorman
2016-06-23 12:44       ` Michal Hocko
2016-06-23 21:45   ` Andrew Morton
2016-06-24  6:35 ` Balbir Singh
2016-06-24  7:50   ` Mel Gorman
2016-06-27 12:48     ` Balbir Singh
  -- strict thread matches above, loose matches on Subject: below --
2016-06-09 18:04 [PATCH 00/27] Move LRU page reclaim from zones to nodes v6 Mel Gorman
2016-06-09 18:04 ` [PATCH 15/27] mm, page_alloc: Consider dirtyable memory in terms of nodes Mel Gorman
2016-06-16 15:45   ` Vlastimil Babka
2016-04-15  9:13 [PATCH 00/27] Move LRU page reclaim from zones to nodes v5 Mel Gorman
2016-04-15  9:13 ` [PATCH 15/27] mm, page_alloc: Consider dirtyable memory in terms of nodes Mel Gorman
2016-04-06 11:19 [RFC PATCH 00/27] Move LRU page reclaim from zones to nodes v3 Mel Gorman
2016-04-06 11:20 ` [PATCH 15/27] mm, page_alloc: Consider dirtyable memory in terms of nodes Mel Gorman

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