From: Barry Song <v-songbaohua@xxxxxxxx> When unplugging a CPU, the current code merges its vm_events with an online CPU. Because, during summation, it only considers online CPUs, which is a crude workaround. By transitioning to summing up all possible CPUs, we can eliminate the need for vm_events_fold_cpu. Suggested-by: Ryan Roberts <ryan.roberts@xxxxxxx> Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx> --- originally suggested by Ryan while he reviewed mTHP counters patchset[1]; I am also applying this suggestion to vm_events -v2: also drop cpus_read_lock() as we don't care about cpu hotplug any more; -v1: https://lore.kernel.org/linux-mm/20240412123039.442743-1-21cnbao@xxxxxxxxx/ [1] https://lore.kernel.org/linux-mm/ca73cbf1-8304-4790-a721-3c3a42f9d293@xxxxxxx/ include/linux/vmstat.h | 5 ----- mm/page_alloc.c | 8 -------- mm/vmstat.c | 21 +-------------------- 3 files changed, 1 insertion(+), 33 deletions(-) diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h index 735eae6e272c..f7eaeb8bfa47 100644 --- a/include/linux/vmstat.h +++ b/include/linux/vmstat.h @@ -83,8 +83,6 @@ static inline void count_vm_events(enum vm_event_item item, long delta) extern void all_vm_events(unsigned long *); -extern void vm_events_fold_cpu(int cpu); - #else /* Disable counters */ @@ -103,9 +101,6 @@ static inline void __count_vm_events(enum vm_event_item item, long delta) static inline void all_vm_events(unsigned long *ret) { } -static inline void vm_events_fold_cpu(int cpu) -{ -} #endif /* CONFIG_VM_EVENT_COUNTERS */ diff --git a/mm/page_alloc.c b/mm/page_alloc.c index cd584aace6bf..8b56d785d587 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5826,14 +5826,6 @@ static int page_alloc_cpu_dead(unsigned int cpu) mlock_drain_remote(cpu); drain_pages(cpu); - /* - * Spill the event counters of the dead processor - * into the current processors event counters. - * This artificially elevates the count of the current - * processor. - */ - vm_events_fold_cpu(cpu); - /* * Zero the differential counters of the dead processor * so that the vm statistics are consistent. diff --git a/mm/vmstat.c b/mm/vmstat.c index db79935e4a54..aaa32418652e 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -114,7 +114,7 @@ static void sum_vm_events(unsigned long *ret) memset(ret, 0, NR_VM_EVENT_ITEMS * sizeof(unsigned long)); - for_each_online_cpu(cpu) { + for_each_possible_cpu(cpu) { struct vm_event_state *this = &per_cpu(vm_event_states, cpu); for (i = 0; i < NR_VM_EVENT_ITEMS; i++) @@ -129,29 +129,10 @@ static void sum_vm_events(unsigned long *ret) */ void all_vm_events(unsigned long *ret) { - cpus_read_lock(); sum_vm_events(ret); - cpus_read_unlock(); } EXPORT_SYMBOL_GPL(all_vm_events); -/* - * Fold the foreign cpu events into our own. - * - * This is adding to the events on one processor - * but keeps the global counts constant. - */ -void vm_events_fold_cpu(int cpu) -{ - struct vm_event_state *fold_state = &per_cpu(vm_event_states, cpu); - int i; - - for (i = 0; i < NR_VM_EVENT_ITEMS; i++) { - count_vm_events(i, fold_state->event[i]); - fold_state->event[i] = 0; - } -} - #endif /* CONFIG_VM_EVENT_COUNTERS */ /* -- 2.34.1
