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>
---
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.
mm/swap.c | 39 ++++++++++++++++++++++++++++++++++++++-
1 file changed, 38 insertions(+), 1 deletion(-)
diff --git a/mm/swap.c b/mm/swap.c
index 4a1d0d2..f42561a 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);
@@ -683,7 +693,34 @@ static void lru_add_drain_per_cpu(struct work_struct *dummy)
*/
int lru_add_drain_all(void)
{
- return schedule_on_each_cpu(lru_add_drain_per_cpu);
+ cpumask_var_t mask;
+ int cpu, rc;
+
+ if (!alloc_cpumask_var(&mask, GFP_KERNEL))
+ return -ENOMEM;
+ cpumask_clear(mask);
+ get_online_cpus();
+
+ /*
+ * Figure out which cpus need flushing. It's OK if we race
+ * with changes to the per-cpu lru pvecs, since it's no worse
+ * than if we flushed all cpus, since a cpu could still end
+ * up putting pages back on its pvec before we returned.
+ * And this avoids interrupting other cpus unnecessarily.
+ */
+ for_each_online_cpu(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))
+ cpumask_set_cpu(cpu, mask);
+ }
+
+ rc = schedule_on_cpu_mask(lru_add_drain_per_cpu, mask);
+
+ put_online_cpus();
+ free_cpumask_var(mask);
+ return rc;
}
/*
--
1.8.3.1
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