This change makes lru_add_drain_all() only selectively interrupt
the cpus that have per-cpu free pages that can be drained.
This is important in nohz mode where calling mlockall(), for
example, otherwise will interrupt every core unnecessarily.
Signed-off-by: Chris Metcalf <cmetcalf@xxxxxxxxxx>
Reviewed-by: Tejun Heo <tj@xxxxxxxxxx>
---
v8: Here's an actual git patch after Tejun's review.
Pull everything inline into lru_add_drain_all(), and use
a mutex plus build-time allocated work_structs to avoid allocation.
v7: try a version with callbacks instead of cpu masks.
Either this or v6 seem like reasonable solutions.
v6: add Tejun's Acked-by, and add missing get/put_cpu_online to
lru_add_drain_all().
v5: provide validity checking on the cpumask for schedule_on_cpu_mask.
By providing an all-or-nothing EINVAL check, we impose the requirement
that the calling code actually know clearly what it's trying to do.
(Note: no change to the mm/swap.c commit)
v4: don't lose possible -ENOMEM in schedule_on_each_cpu()
(Note: no change to the mm/swap.c commit)
v3: split commit into two, one for workqueue and one for mm, though both
should probably be taken through -mm.
include/linux/swap.h | 2 +-
mm/swap.c | 44 +++++++++++++++++++++++++++++++++++++++-----
2 files changed, 40 insertions(+), 6 deletions(-)
diff --git a/include/linux/swap.h b/include/linux/swap.h
index d95cde5..acea8e0 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -247,7 +247,7 @@ extern void activate_page(struct page *);
extern void mark_page_accessed(struct page *);
extern void lru_add_drain(void);
extern void lru_add_drain_cpu(int cpu);
-extern int lru_add_drain_all(void);
+extern void lru_add_drain_all(void);
extern void rotate_reclaimable_page(struct page *page);
extern void deactivate_page(struct page *page);
extern void swap_setup(void);
diff --git a/mm/swap.c b/mm/swap.c
index 4a1d0d2..8d19543 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -405,6 +405,11 @@ static void activate_page_drain(int cpu)
pagevec_lru_move_fn(pvec, __activate_page, NULL);
}
+static bool need_activate_page_drain(int cpu)
+{
+ return pagevec_count(&per_cpu(activate_page_pvecs, cpu)) != 0;
+}
+
void activate_page(struct page *page)
{
if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
@@ -422,6 +427,11 @@ static inline void activate_page_drain(int cpu)
{
}
+static bool need_activate_page_drain(int cpu)
+{
+ return false;
+}
+
void activate_page(struct page *page)
{
struct zone *zone = page_zone(page);
@@ -678,12 +688,36 @@ static void lru_add_drain_per_cpu(struct work_struct *dummy)
lru_add_drain();
}
-/*
- * Returns 0 for success
- */
-int lru_add_drain_all(void)
+static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
+
+void lru_add_drain_all(void)
{
- return schedule_on_each_cpu(lru_add_drain_per_cpu);
+ static DEFINE_MUTEX(lock);
+ static struct cpumask has_work;
+ int cpu;
+
+ mutex_lock(&lock);
+ get_online_cpus();
+ cpumask_clear(&has_work);
+
+ for_each_online_cpu(cpu) {
+ struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);
+
+ if (pagevec_count(&per_cpu(lru_add_pvec, cpu)) ||
+ pagevec_count(&per_cpu(lru_rotate_pvecs, cpu)) ||
+ pagevec_count(&per_cpu(lru_deactivate_pvecs, cpu)) ||
+ need_activate_page_drain(cpu)) {
+ INIT_WORK(work, lru_add_drain_per_cpu);
+ schedule_work_on(cpu, work);
+ cpumask_set_cpu(cpu, &has_work);
+ }
+ }
+
+ for_each_cpu(cpu, &has_work)
+ flush_work(&per_cpu(lru_add_drain_work, cpu));
+
+ put_online_cpus();
+ mutex_unlock(&lock);
}
/*
--
1.8.3.1
--
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