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mm, page_alloc: fix dirtyable highmem calculation

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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: Minchan Kim <minchan@kernel.org>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Minchan Kim 2016-07-28 15:47:08 -07:00 committed by Linus Torvalds
parent bca6759258
commit 9cb937e219
1 changed files with 10 additions and 6 deletions
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16
mm/page-writeback.c
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@ -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