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mm, sysctl: make NUMA stats configurable

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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]>
This commit is contained in:
Kemi Wang 2017-11-15 17:38:22 -08:00 • committed by Linus Torvalds
commit 4518085e12
6 changed files with 115 additions and 0 deletions
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71
mm/vmstat.c
View file

@ -32,6 +32,77 @@
#define NUMA_STATS_THRESHOLD (U16_MAX - 2)
#ifdef CONFIG_NUMA
int sysctl_vm_numa_stat = ENABLE_NUMA_STAT;
/* zero numa counters within a zone */
static void zero_zone_numa_counters(struct zone *zone)
{
int item, cpu;
for (item = 0; item < NR_VM_NUMA_STAT_ITEMS; item++) {
atomic_long_set(&zone->vm_numa_stat[item], 0);
for_each_online_cpu(cpu)
per_cpu_ptr(zone->pageset, cpu)->vm_numa_stat_diff[item]
= 0;
}
}
/* zero numa counters of all the populated zones */
static void zero_zones_numa_counters(void)
{
struct zone *zone;
for_each_populated_zone(zone)
zero_zone_numa_counters(zone);
}
/* zero global numa counters */
static void zero_global_numa_counters(void)
{
int item;
for (item = 0; item < NR_VM_NUMA_STAT_ITEMS; item++)
atomic_long_set(&vm_numa_stat[item], 0);
}
static void invalid_numa_statistics(void)
{
zero_zones_numa_counters();
zero_global_numa_counters();
}
static DEFINE_MUTEX(vm_numa_stat_lock);
int sysctl_vm_numa_stat_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *length, loff_t *ppos)
{
int ret, oldval;
mutex_lock(&vm_numa_stat_lock);
if (write)
oldval = sysctl_vm_numa_stat;
ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
if (ret || !write)
goto out;
if (oldval == sysctl_vm_numa_stat)
goto out;
else if (sysctl_vm_numa_stat == ENABLE_NUMA_STAT) {
static_branch_enable(&vm_numa_stat_key);
pr_info("enable numa statistics\n");
} else {
static_branch_disable(&vm_numa_stat_key);
invalid_numa_statistics();
pr_info("disable numa statistics, and clear numa counters\n");
}
out:
mutex_unlock(&vm_numa_stat_lock);
return ret;
}
#endif
#ifdef CONFIG_VM_EVENT_COUNTERS
DEFINE_PER_CPU(struct vm_event_state, vm_event_states) = {{0}};
EXPORT_PER_CPU_SYMBOL(vm_event_states);