diff options
| author | Mel Gorman <mgorman@suse.de> | 2014-04-23 08:27:15 +1000 |
|---|---|---|
| committer | Stephen Rothwell <sfr@canb.auug.org.au> | 2014-04-23 08:27:15 +1000 |
| commit | d4dfbd52f08d8487de1033a2958b67d7ab1aa89f (patch) | |
| tree | f6ae9f6125348049ddb07c8969792f659ba03c58 /mm | |
| parent | c92148898c3120219c50f87a2c52c6d3579816ca (diff) | |
mm: disable zone_reclaim_mode by default
When it was introduced, zone_reclaim_mode made sense as NUMA distances
punished and workloads were generally partitioned to fit into a NUMA node.
NUMA machines are now common but few of the workloads are NUMA-aware and
it's routine to see major performance degradation due to zone_reclaim_mode
being enabled but relatively few can identify the problem.
Those that require zone_reclaim_mode are likely to be able to detect when
it needs to be enabled and tune appropriately so lets have a sensible
default for the bulk of users.
This patch (of 2):
zone_reclaim_mode causes processes to prefer reclaiming memory from local
node instead of spilling over to other nodes. This made sense initially when
NUMA machines were almost exclusively HPC and the workload was partitioned
into nodes. The NUMA penalties were sufficiently high to justify reclaiming
the memory. On current machines and workloads it is often the case that
zone_reclaim_mode destroys performance but not all users know how to detect
this. Favour the common case and disable it by default. Users that are
sophisticated enough to know they need zone_reclaim_mode will detect it.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/page_alloc.c | 2 |
1 files changed, 0 insertions, 2 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 7cfdcd808f52..dfe954fbb48a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1860,8 +1860,6 @@ static void __paginginit init_zone_allows_reclaim(int nid) for_each_node_state(i, N_MEMORY) if (node_distance(nid, i) <= RECLAIM_DISTANCE) node_set(i, NODE_DATA(nid)->reclaim_nodes); - else - zone_reclaim_mode = 1; } #else /* CONFIG_NUMA */ |