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authorGavin Shan <gwshan@linux.vnet.ibm.com>2017-02-24 14:59:33 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-03-12 06:41:43 +0100
commitd1e8042628a31e28c8e92411ab83a28bd5e3f7c9 (patch)
treef6df2cf341869e00c84e02442be7309f06f7e024
parentf1faaec4843a6bfcb795887f5b1a280fb874789d (diff)
mm/page_alloc: fix nodes for reclaim in fast path
commit e02dc017c3032dcdce1b993af0db135462e1b4b7 upstream. When @node_reclaim_node isn't 0, the page allocator tries to reclaim pages if the amount of free memory in the zones are below the low watermark. On Power platform, none of NUMA nodes are scanned for page reclaim because no nodes match the condition in zone_allows_reclaim(). On Power platform, RECLAIM_DISTANCE is set to 10 which is the distance of Node-A to Node-A. So the preferred node even won't be scanned for page reclaim. __alloc_pages_nodemask() get_page_from_freelist() zone_allows_reclaim() Anton proposed the test code as below: # cat alloc.c : int main(int argc, char *argv[]) { void *p; unsigned long size; unsigned long start, end; start = time(NULL); size = strtoul(argv[1], NULL, 0); printf("To allocate %ldGB memory\n", size); size <<= 30; p = malloc(size); assert(p); memset(p, 0, size); end = time(NULL); printf("Used time: %ld seconds\n", end - start); sleep(3600); return 0; } The system I use for testing has two NUMA nodes. Both have 128GB memory. In below scnario, the page caches on node#0 should be reclaimed when it encounters pressure to accommodate request of allocation. # echo 2 > /proc/sys/vm/zone_reclaim_mode; \ sync; \ echo 3 > /proc/sys/vm/drop_caches; \ # taskset -c 0 cat file.32G > /dev/null; \ grep FilePages /sys/devices/system/node/node0/meminfo Node 0 FilePages: 33619712 kB # taskset -c 0 ./alloc 128 # grep FilePages /sys/devices/system/node/node0/meminfo Node 0 FilePages: 33619840 kB # grep MemFree /sys/devices/system/node/node0/meminfo Node 0 MemFree: 186816 kB With the patch applied, the pagecache on node-0 is reclaimed when its free memory is running out. It's the expected behaviour. # echo 2 > /proc/sys/vm/zone_reclaim_mode; \ sync; \ echo 3 > /proc/sys/vm/drop_caches # taskset -c 0 cat file.32G > /dev/null; \ grep FilePages /sys/devices/system/node/node0/meminfo Node 0 FilePages: 33605568 kB # taskset -c 0 ./alloc 128 # grep FilePages /sys/devices/system/node/node0/meminfo Node 0 FilePages: 1379520 kB # grep MemFree /sys/devices/system/node/node0/meminfo Node 0 MemFree: 317120 kB Fixes: 5f7a75acdb24 ("mm: page_alloc: do not cache reclaim distances") Link: http://lkml.kernel.org/r/1486532455-29613-1-git-send-email-gwshan@linux.vnet.ibm.com Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com> Acked-by: Mel Gorman <mgorman@suse.de> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Anton Blanchard <anton@samba.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--mm/page_alloc.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f4a02e240fb6..1460e6ad5e14 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2858,7 +2858,7 @@ bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
#ifdef CONFIG_NUMA
static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
{
- return node_distance(zone_to_nid(local_zone), zone_to_nid(zone)) <
+ return node_distance(zone_to_nid(local_zone), zone_to_nid(zone)) <=
RECLAIM_DISTANCE;
}
#else /* CONFIG_NUMA */