leds: ledtrig-activity: Add a system activity LED trigger

The "activity" trigger was inspired by the heartbeat one, but aims at
providing instant indication of the immediate CPU usage. Under idle
condition, it flashes 10ms every second. At 100% usage, it flashes
90ms every 100ms. The blinking frequency increases from 1 to 10 Hz
until either the load is high enough to saturate one CPU core or 50%
load is reached on a single-core system. Then past this point only the
duty cycle increases from 10 to 90%.

This results in a very visible activity reporting allowing one to
immediately tell whether a machine is under load or not, making it
quite suitable to be used in clusters.

Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
index 3f9ddb9fafa7..bb090216b4dc 100644
--- a/drivers/leds/trigger/Kconfig
+++ b/drivers/leds/trigger/Kconfig
@@ -77,6 +77,15 @@ config LEDS_TRIGGER_CPU
 
 	  If unsure, say N.
 
+config LEDS_TRIGGER_ACTIVITY
+	tristate "LED activity Trigger"
+	depends on LEDS_TRIGGERS
+	help
+	  This allows LEDs to be controlled by a immediate CPU usage.
+	  The flash frequency and duty cycle varies from faint flashes to
+	  intense brightness depending on the instant CPU load.
+	  If unsure, say N.
+
 config LEDS_TRIGGER_GPIO
 	tristate "LED GPIO Trigger"
 	depends on LEDS_TRIGGERS