mm, sysctl: make NUMA stats configurable
This is the second step which introduces a tunable interface that allow
numa stats configurable for optimizing zone_statistics(), as suggested
by Dave Hansen and Ying Huang.
=========================================================================
When page allocation performance becomes a bottleneck and you can
tolerate some possible tool breakage and decreased numa counter
precision, you can do:
echo 0 > /proc/sys/vm/numa_stat
In this case, numa counter update is ignored. We can see about
*4.8%*(185->176) drop of cpu cycles per single page allocation and
reclaim on Jesper's page_bench01 (single thread) and *8.1%*(343->315)
drop of cpu cycles per single page allocation and reclaim on Jesper's
page_bench03 (88 threads) running on a 2-Socket Broadwell-based server
(88 threads, 126G memory).
Benchmark link provided by Jesper D Brouer (increase loop times to
10000000):
https://github.com/netoptimizer/prototype-kernel/tree/master/kernel/mm/bench
=========================================================================
When page allocation performance is not a bottleneck and you want all
tooling to work, you can do:
echo 1 > /proc/sys/vm/numa_stat
This is system default setting.
Many thanks to Michal Hocko, Dave Hansen, Ying Huang and Vlastimil Babka
for comments to help improve the original patch.
[[email protected]: make sure mutex is a global static]
Link: http://lkml.kernel.org/r/20171107213809.GA4314@beast
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Kemi Wang <[email protected]>
Signed-off-by: Kees Cook <[email protected]>
Reported-by: Jesper Dangaard Brouer <[email protected]>
Suggested-by: Dave Hansen <[email protected]>
Suggested-by: Ying Huang <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: "Luis R . Rodriguez" <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Christopher Lameter <[email protected]>
Cc: Sebastian Andrzej Siewior <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Tim Chen <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Aaron Lu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7ca668e..67f523c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -82,6 +82,8 @@ DEFINE_PER_CPU(int, numa_node);
EXPORT_PER_CPU_SYMBOL(numa_node);
#endif
+DEFINE_STATIC_KEY_TRUE(vm_numa_stat_key);
+
#ifdef CONFIG_HAVE_MEMORYLESS_NODES
/*
* N.B., Do NOT reference the '_numa_mem_' per cpu variable directly.
@@ -2777,6 +2779,10 @@ static inline void zone_statistics(struct zone *preferred_zone, struct zone *z)
#ifdef CONFIG_NUMA
enum numa_stat_item local_stat = NUMA_LOCAL;
+ /* skip numa counters update if numa stats is disabled */
+ if (!static_branch_likely(&vm_numa_stat_key))
+ return;
+
if (z->node != numa_node_id())
local_stat = NUMA_OTHER;
