On Wed 18-10-17 09:42:07, Kemi Wang wrote: > 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: > V4->V5 > a) Scope vm_numa_stat_lock into the sysctl handler function, as suggested > by Michal Hocko; > b) Only allow 0/1 value when setting a value to numa_stat at userspace, > that would keep the possibility for add auto mode in future (e.g. 2 for > auto mode), as suggested by Michal Hocko. > > 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> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Thanks! > --- > Documentation/sysctl/vm.txt | 16 +++++++++++ > include/linux/vmstat.h | 10 +++++++ > kernel/sysctl.c | 9 ++++++ > mm/mempolicy.c | 3 ++ > mm/page_alloc.c | 6 ++++ > mm/vmstat.c | 70 +++++++++++++++++++++++++++++++++++++++++++++ > 6 files changed, 114 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..8f272db 100644 > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -1371,6 +1371,15 @@ 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, > + .extra1 = &zero, > + .extra2 = &one, > + }, > #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..1faf30d 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; > + > +/* 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; > + DEFINE_MUTEX(vm_numa_stat_lock); > + > + 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); > -- > 2.7.4 > -- Michal Hocko SUSE Labs
