| Message ID | 1338553446-22292-1-git-send-email-anton.vorontsov@linaro.org |
|---|---|
| State | New |
| Headers | show |
On Fri, 1 Jun 2012, Anton Vorontsov wrote: > This function forcibly flushes per-cpu vmstat diff counters to the > global counters. Why is it necessary to have a function that does not expire the pcps? Is that side effect important? We use refresh_vm_cpu_stats(cpu) in page_alloc.c already to flush the vmstat counters. Is the flushing of the pcps in 2 seconds insteads of 3 once really that important? Also if we do this Can we therefore also name the function in a different way like flush_vmstats() > @@ -456,11 +457,15 @@ void refresh_cpu_vm_stats(int cpu) > local_irq_restore(flags); > atomic_long_add(v, &zone->vm_stat[i]); > global_diff[i] += v; > + if (!drain_pcp) > + continue; > #ifdef CONFIG_NUMA > /* 3 seconds idle till flush */ > p->expire = 3; > #endif Erm. This should be #ifdef CONFIG_NUMA if (drain_pcp) p->expire = 3; #endif The construct using "continue" is weird. > } > + if (!drain_pcp) > + continue; > cond_resched(); > #ifdef CONFIG_NUMA > /* > @@ -495,6 +500,21 @@ void refresh_cpu_vm_stats(int cpu) > atomic_long_add(global_diff[i], &vm_stat[i]); > } > > +void refresh_cpu_vm_stats(int cpu) > +{ > + __refresh_cpu_vm_stats(cpu, 1); > +} Fold __refresh_cpu_vm_stats into this function and modify the caller of refresh_cpu_vm_stats instead.
(6/1/12 8:24 AM), Anton Vorontsov wrote: > This function forcibly flushes per-cpu vmstat diff counters to the > global counters. > > Note that we don't try to flush percpu pagesets, the pcp will be > still flushed once per 3 seconds. > > Signed-off-by: Anton Vorontsov<anton.vorontsov@linaro.org> No. This is insane. Your patch improved vmevent accuracy a _bit_. But instead of, decrease a performance of large systems. That's no good deal. 99% user never uses vmevent. MOREOVER, this patch don't solve vmevent accuracy issue AT ALL. because of, a second is enough big to make large inaccuracy. Modern cpus are fast. Guys, the fact is, user land monitor can't use implicit batch likes vmstat. That's a reason why perf don't use vmstat. I suggest you see perf APIs. It may bring you good inspiration.
diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h index 65efb92..2a53896 100644 --- a/include/linux/vmstat.h +++ b/include/linux/vmstat.h @@ -200,6 +200,7 @@ extern void __inc_zone_state(struct zone *, enum zone_stat_item); extern void dec_zone_state(struct zone *, enum zone_stat_item); extern void __dec_zone_state(struct zone *, enum zone_stat_item); +void refresh_vm_stats(void); void refresh_cpu_vm_stats(int); void refresh_zone_stat_thresholds(void); @@ -253,6 +254,7 @@ static inline void __dec_zone_page_state(struct page *page, #define set_pgdat_percpu_threshold(pgdat, callback) { } +static inline void refresh_vm_stats(void) { } static inline void refresh_cpu_vm_stats(int cpu) { } static inline void refresh_zone_stat_thresholds(void) { } diff --git a/mm/vmstat.c b/mm/vmstat.c index f600557..4a9d432 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -13,6 +13,7 @@ #include <linux/err.h> #include <linux/module.h> #include <linux/slab.h> +#include <linux/smp.h> #include <linux/cpu.h> #include <linux/vmstat.h> #include <linux/sched.h> @@ -434,7 +435,7 @@ EXPORT_SYMBOL(dec_zone_page_state); * with the global counters. These could cause remote node cache line * bouncing and will have to be only done when necessary. */ -void refresh_cpu_vm_stats(int cpu) +static void __refresh_cpu_vm_stats(int cpu, bool drain_pcp) { struct zone *zone; int i; @@ -456,11 +457,15 @@ void refresh_cpu_vm_stats(int cpu) local_irq_restore(flags); atomic_long_add(v, &zone->vm_stat[i]); global_diff[i] += v; + if (!drain_pcp) + continue; #ifdef CONFIG_NUMA /* 3 seconds idle till flush */ p->expire = 3; #endif } + if (!drain_pcp) + continue; cond_resched(); #ifdef CONFIG_NUMA /* @@ -495,6 +500,21 @@ void refresh_cpu_vm_stats(int cpu) atomic_long_add(global_diff[i], &vm_stat[i]); } +void refresh_cpu_vm_stats(int cpu) +{ + __refresh_cpu_vm_stats(cpu, 1); +} + +static void smp_call_refresh_cpu_vm_stats(void *info) +{ + __refresh_cpu_vm_stats(smp_processor_id(), 0); +} + +void refresh_vm_stats(void) +{ + smp_call_function(smp_call_refresh_cpu_vm_stats, NULL, 1); +} + #endif #ifdef CONFIG_NUMA
This function forcibly flushes per-cpu vmstat diff counters to the global counters. Note that we don't try to flush percpu pagesets, the pcp will be still flushed once per 3 seconds. Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org> --- include/linux/vmstat.h | 2 ++ mm/vmstat.c | 22 +++++++++++++++++++++- 2 files changed, 23 insertions(+), 1 deletion(-)