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Commit 9cb937e2 authored by Minchan Kim's avatar Minchan Kim Committed by Linus Torvalds
Browse files

mm, page_alloc: fix dirtyable highmem calculation 

When I tested vmscale in mmtest in 32bit, I found the benchmark was slow
down 0.5 times.

                base        node
                   1    global-1
User           12.98       16.04
System        147.61      166.42
Elapsed        26.48       38.08

With vmstat, I found IO wait avg is much increased compared to base.

The reason was highmem_dirtyable_memory accumulates free pages and
highmem_file_pages from HIGHMEM to MOVABLE zones which was wrong.  With
that, dirth_thresh in throtlle_vm_write is always 0 so that it calls
congestion_wait frequently if writeback starts.

With this patch, it is much recovered.

                base        node          fi
                   1    global-1         fix
User           12.98       16.04       13.78
System        147.61      166.42      143.92
Elapsed        26.48       38.08       29.64

Link: http://lkml.kernel.org/r/1468404004-5085-4-git-send-email-mgorman@techsingularity.net


Signed-off-by: default avatarMinchan Kim <minchan@kernel.org>
Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent bca67592

mm/page-writeback.c

+10 −6
Original line number Diff line number Diff line
@@ -307,27 +307,31 @@ static unsigned long highmem_dirtyable_memory(unsigned long total) 
{

#ifdef CONFIG_HIGHMEM

	int node;

	unsigned long x = 0;

	unsigned long x;

	int i;

	unsigned long dirtyable = atomic_read(&highmem_file_pages);

	unsigned long dirtyable = 0;



	for_each_node_state(node, N_HIGH_MEMORY) {

		for (i = ZONE_NORMAL + 1; i < MAX_NR_ZONES; i++) {

			struct zone *z;

			unsigned long nr_pages;



			if (!is_highmem_idx(i))

				continue;



			z = &NODE_DATA(node)->node_zones[i];

			dirtyable += zone_page_state(z, NR_FREE_PAGES);

			if (!populated_zone(z))

				continue;



			nr_pages = zone_page_state(z, NR_FREE_PAGES);

			/* watch for underflows */

			dirtyable -= min(dirtyable, high_wmark_pages(z));



			x += dirtyable;

			nr_pages -= min(nr_pages, high_wmark_pages(z));

			dirtyable += nr_pages;

		}

	}



	x = dirtyable + atomic_read(&highmem_file_pages);



	/*

	 * Unreclaimable memory (kernel memory or anonymous memory

	 * without swap) can bring down the dirtyable pages below