[PATCH] acpi/ghes: load balance timers

[Li RongQing <lirongqing@xxxxxxxxx>]

Kernel needs to set up a timer for each poll type notification, On
some system, these are tens of thousands of timers, which expires
periodically and preempt one CPU which calls ghes_probe at boot stage

so load balance evenly timers to all online cpus, reduce task jitter

Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx>
---
 drivers/acpi/apei/ghes.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index ab2a82c..7bc7053 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -934,9 +934,10 @@ static int ghes_proc(struct ghes *ghes)
 	return rc;
 }
 
-static void ghes_add_timer(struct ghes *ghes)
+static void ghes_add_timer(struct ghes *ghes, bool probe)
 {
 	struct acpi_hest_generic *g = ghes->generic;
+	static int cpu_running_timer;
 	unsigned long expire;
 
 	if (!g->notify.poll_interval) {
@@ -946,7 +947,16 @@ static void ghes_add_timer(struct ghes *ghes)
 	}
 	expire = jiffies + msecs_to_jiffies(g->notify.poll_interval);
 	ghes->timer.expires = round_jiffies_relative(expire);
-	add_timer(&ghes->timer);
+
+	if (probe) {
+		cpu_running_timer = cpumask_next(cpu_running_timer, cpu_online_mask);
+		if (cpu_running_timer >= nr_cpu_ids)
+			cpu_running_timer = cpumask_first(cpu_online_mask);
+
+		add_timer_on(&ghes->timer, cpu_running_timer);
+	} else {
+		add_timer_on(&ghes->timer, raw_smp_processor_id());
+	}
 }
 
 static void ghes_poll_func(struct timer_list *t)
@@ -958,7 +968,7 @@ static void ghes_poll_func(struct timer_list *t)
 	ghes_proc(ghes);
 	spin_unlock_irqrestore(&ghes_notify_lock_irq, flags);
 	if (!(ghes->flags & GHES_EXITING))
-		ghes_add_timer(ghes);
+		ghes_add_timer(ghes, false);
 }
 
 static irqreturn_t ghes_irq_func(int irq, void *data)
@@ -1388,7 +1398,7 @@ static int ghes_probe(struct platform_device *ghes_dev)
 	switch (generic->notify.type) {
 	case ACPI_HEST_NOTIFY_POLLED:
 		timer_setup(&ghes->timer, ghes_poll_func, 0);
-		ghes_add_timer(ghes);
+		ghes_add_timer(ghes, true);
 		break;
 	case ACPI_HEST_NOTIFY_EXTERNAL:
 		/* External interrupt vector is GSI */
-- 
2.9.4