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. ChangeLog: V3->V4 a) Get rid of auto mode of numa stats, and may add it back if necessary, as alignment before; b) Skip NUMA_INTERLEAVE_HIT counter update when numa stats is disabled, as reported by Andrey Ryabinin. See commit "de55c8b2519" for details c) Remove extern declaration for those clear_numa_ function, and make them static in vmstat.c, as suggested by Vlastimil Babka. V2->V3: a) Propose a better way to use jump label to eliminate the overhead of branch selection in zone_statistics(), as inspired by Ying Huang; b) Add a paragraph in commit log to describe the way for branch target selection; c) Use a more descriptive name numa_stats_mode instead of vmstat_mode, and change the description accordingly, as suggested by Michal Hocko; d) Make this functionality NUMA-specific via ifdef V1->V2: a) Merge to one patch; b) Use jump label to eliminate the overhead of branch selection; c) Add a single-time log message at boot time to help tell users what happened. Reported-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx> Suggested-by: Dave Hansen <dave.hansen@xxxxxxxxx> Suggested-by: Ying Huang <ying.huang@xxxxxxxxx> Signed-off-by: Kemi Wang <kemi.wang@xxxxxxxxx> --- Documentation/sysctl/vm.txt | 16 +++++++++++ include/linux/vmstat.h | 10 +++++++ kernel/sysctl.c | 7 +++++ mm/mempolicy.c | 3 ++ mm/page_alloc.c | 6 ++++ mm/vmstat.c | 70 +++++++++++++++++++++++++++++++++++++++++++++ 6 files changed, 112 insertions(+) diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt index 9baf66a..f65c5c7 100644 --- a/Documentation/sysctl/vm.txt +++ b/Documentation/sysctl/vm.txt @@ -58,6 +58,7 @@ Currently, these files are in /proc/sys/vm: - percpu_pagelist_fraction - stat_interval - stat_refresh +- numa_stat - swappiness - user_reserve_kbytes - vfs_cache_pressure @@ -792,6 +793,21 @@ with no ill effects: errors and warnings on these stats are suppressed.) ============================================================== +numa_stat + +This interface allows runtime configuration of numa statistics. + +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 + +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 + +============================================================== + swappiness This control is used to define how aggressive the kernel will swap diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h index ade7cb5..c605c94 100644 --- a/include/linux/vmstat.h +++ b/include/linux/vmstat.h @@ -6,9 +6,19 @@ #include <linux/mmzone.h> #include <linux/vm_event_item.h> #include <linux/atomic.h> +#include <linux/static_key.h> extern int sysctl_stat_interval; +#ifdef CONFIG_NUMA +#define ENABLE_NUMA_STAT 1 +#define DISABLE_NUMA_STAT 0 +extern int sysctl_vm_numa_stat; +DECLARE_STATIC_KEY_TRUE(vm_numa_stat_key); +extern int sysctl_vm_numa_stat_handler(struct ctl_table *table, + int write, void __user *buffer, size_t *length, loff_t *ppos); +#endif + #ifdef CONFIG_VM_EVENT_COUNTERS /* * Light weight per cpu counter implementation. diff --git a/kernel/sysctl.c b/kernel/sysctl.c index d9c31bc..f6a79a3 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1371,6 +1371,13 @@ static struct ctl_table vm_table[] = { .mode = 0644, .proc_handler = &hugetlb_mempolicy_sysctl_handler, }, + { + .procname = "numa_stat", + .data = &sysctl_vm_numa_stat, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = sysctl_vm_numa_stat_handler, + }, #endif { .procname = "hugetlb_shm_group", diff --git a/mm/mempolicy.c b/mm/mempolicy.c index a2af6d5..78344cf 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1920,6 +1920,9 @@ static struct page *alloc_page_interleave(gfp_t gfp, unsigned order, struct page *page; page = __alloc_pages(gfp, order, nid); + /* skip NUMA_INTERLEAVE_HIT counter update if numa stats is disabled */ + if (!static_branch_likely(&vm_numa_stat_key)) + return page; if (page && page_to_nid(page) == nid) { preempt_disable(); __inc_numa_state(page_zone(page), NUMA_INTERLEAVE_HIT); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 77e4d3c..7bdb4f7 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -83,6 +83,8 @@ 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. @@ -2743,6 +2745,10 @@ 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; diff --git a/mm/vmstat.c b/mm/vmstat.c index 4bb13e7..e746ed1 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -32,6 +32,76 @@ #define NUMA_STATS_THRESHOLD (U16_MAX - 2) +#ifdef CONFIG_NUMA +int sysctl_vm_numa_stat = ENABLE_NUMA_STAT; +static DEFINE_MUTEX(vm_numa_stat_lock); + +/* 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(); +} + +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(table, write, buffer, length, ppos); + if (ret || !write) + goto out; + + if (oldval == sysctl_vm_numa_stat) + goto out; + else if (oldval == DISABLE_NUMA_STAT) { + static_branch_enable(&vm_numa_stat_key); + pr_info("enable numa statistics\n"); + } else if (sysctl_vm_numa_stat == DISABLE_NUMA_STAT) { + 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); -- 2.7.4
