From: Barry Song <21cnbao@gmail.com>
To: akpm@linux-foundation.org, linux-mm@kvack.org, ryan.roberts@arm.com
Cc: hannes@cmpxchg.org, linux-kernel@vger.kernel.org,
david@redhat.com, v-songbaohua@oppo.com, vbabka@suse.cz,
willy@infradead.org
Subject: [PATCH v2] mm/vmstat: sum up all possible CPUs instead of using vm_events_fold_cpu
Date: Fri, 3 May 2024 14:09:24 +1200 [thread overview]
Message-ID: <20240503020924.208431-1-21cnbao@gmail.com> (raw)
From: Barry Song <v-songbaohua@oppo.com>
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@arm.com>
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
---
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@gmail.com/
[1] https://lore.kernel.org/linux-mm/ca73cbf1-8304-4790-a721-3c3a42f9d293@arm.com/
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
next reply other threads:[~2024-05-03 2:09 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-03 2:09 Barry Song [this message]
2024-05-03 9:16 ` [PATCH v2] mm/vmstat: sum up all possible CPUs instead of using vm_events_fold_cpu Ryan Roberts
2024-05-03 10:17 ` Barry Song
2024-05-03 10:52 ` Ryan Roberts
2024-05-03 13:45 ` Vlastimil Babka
2024-05-03 14:14 ` Ryan Roberts
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