[PATCH v6 19/23] virt/steal_monitor: Provide default method to get num of CPUs for steal ratio

[Shrikanth Hegde]

This method informs the steal_monitor core, how many CPUs it needs to
consider for steal ratio calculations.
steal_ratio = (delta_steal * 100 * 100) / (delta_ns * number_of_cpus);

Default method returns number of Active CPUs since it calculates steal
time across active CPUs.

Signed-off-by: Shrikanth Hegde <sshegde@xxxxxxxxxxxxx>
---
v5->v6:
- Add cpus_read_lock() for hotplug safety.

 drivers/virt/steal_monitor/defaults.c | 11 +++++++++++
 drivers/virt/steal_monitor/sm_core.h  |  1 +
 2 files changed, 12 insertions(+)

diff --git a/drivers/virt/steal_monitor/defaults.c b/drivers/virt/steal_monitor/defaults.c
index 4e2e5b233948..70dcfb1ce4cb 100644
--- a/drivers/virt/steal_monitor/defaults.c
+++ b/drivers/virt/steal_monitor/defaults.c
@@ -27,6 +27,17 @@ u64 __weak get_system_steal_time(void)
 	return total_steal;
 }
 
+/*
+ * Return number of CPUs to consider for steal ratio calculation
+ *
+ * Default returns number of active CPUs.
+ */
+unsigned int __weak get_num_cpus_steal_ratio(void)
+{
+	guard(cpus_read_lock)();
+	return num_active_cpus();
+}
+
 /*
  * Default implementation of decrementing the preferred CPUs based on steal
  * time. This is simple logic and decrease the preferred CPUs by 1 core.
diff --git a/drivers/virt/steal_monitor/sm_core.h b/drivers/virt/steal_monitor/sm_core.h
index 030f6236c38e..794d3be04248 100644
--- a/drivers/virt/steal_monitor/sm_core.h
+++ b/drivers/virt/steal_monitor/sm_core.h
@@ -26,6 +26,7 @@ struct steal_monitor {
 extern struct steal_monitor sm_core_ctx;
 
 u64 get_system_steal_time(void);
+unsigned int get_num_cpus_steal_ratio(void);
 void increase_preferred_cpus(struct steal_monitor *ctx);
 void decrease_preferred_cpus(struct steal_monitor *ctx);
 
-- 
2.47.3