[PATCH v5 17/24] virt/steal_monitor: Add control knobs for handling steal values

[Shrikanth Hegde <sshegde@linux.ibm.com>]

These are the knobs to control the steal_monitor.

interval_ms:
How often steal monitor checks for steal time.
(Default: 1000 i.e 1 second)

This controls how fast steal monitor driver reacts to changes to
the contention of physical CPUs. Since it does fair amount of
work, setting too low will have overheads. If set to 0, on next
work it will be set to default.

low_threshold:
lower threshold value in percentage * 100.
(Default: 200, i.e 2% steal is considered as low threshold)

This determines what values should be considered as nil/no steal values.
When steal monitor see steal time is below or equal to this value, it
will increase the preferred CPUs by 1 core. Having value as zero
might cause too much oscillations.

high_threshold:
higher threshold value in percentage * 100
(Default: 500, i.e 5% steal is considered as high threshold)

This determines what values should be considered as high steal values.
When steal monitor sees steal time is higher than this value, it will
reduce the preferred CPUs by 1 core.

Also available at: Documentation/driver-api/steal-monitor.rst

Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
---
v4->v5:
- Modified for steal_monitor

 drivers/virt/steal_monitor/sm_core.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/virt/steal_monitor/sm_core.c b/drivers/virt/steal_monitor/sm_core.c
index 3feb686dd3c4..b95b37e37a16 100644
--- a/drivers/virt/steal_monitor/sm_core.c
+++ b/drivers/virt/steal_monitor/sm_core.c
@@ -14,7 +14,23 @@
 
 #include "sm_core.h"
 
-struct steal_monitor sm_core_ctx;
+struct steal_monitor sm_core_ctx = {
+	.interval_ms = 1000,	/* 1 second */
+	.high_threshold = 500,	/* 5% */
+	.low_threshold = 200,	/* 2% */
+};
+
+module_param_named(interval_ms, sm_core_ctx.interval_ms, uint, 0644);
+MODULE_PARM_DESC(interval_ms,
+		 "Sampling frequency for steal values in milliseconds (default: 1000)");
+
+module_param_named(high_threshold, sm_core_ctx.high_threshold, uint, 0644);
+MODULE_PARM_DESC(high_threshold,
+		 "High steal threshold (default: 500 i.e 5%)");
+
+module_param_named(low_threshold, sm_core_ctx.low_threshold, uint, 0644);
+MODULE_PARM_DESC(low_threshold,
+		 "Low steal threshold (default: 200 i.e 2%)");
 
 static int __init steal_monitor_init(void)
 {
-- 
2.47.3