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authorCarsten Emde <C.Emde@osadl.org>2012-07-19 16:34:10 -0400
committerRafael J. Wysocki <rjw@sisk.pl>2012-09-03 19:35:44 -0400
commit62d6ae880e3e76098d5e345decd2dce443975889 (patch)
tree5788868e10c08030c5981adae8f5dfd6306b2608 /drivers/cpuidle
parent4cbe5a555fa58a79b6ecbb6c531b8bab0650778d (diff)
Honor state disabling in the cpuidle ladder governor
There are two cpuidle governors ladder and menu. While the ladder governor is always available, if CONFIG_CPU_IDLE is selected, the menu governor additionally requires CONFIG_NO_HZ. A particular C state can be disabled by writing to the sysfs file /sys/devices/system/cpu/cpuN/cpuidle/stateN/disable, but this mechanism is only implemented in the menu governor. Thus, in a system where CONFIG_NO_HZ is not selected, the ladder governor becomes default and always will walk through all sleep states - irrespective of whether the C state was disabled via sysfs or not. The only way to select a specific C state was to write the related latency to /dev/cpu_dma_latency and keep the file open as long as this setting was required - not very practical and not suitable for setting a single core in an SMP system. With this patch, the ladder governor only will promote to the next C state, if it has not been disabled, and it will demote, if the current C state was disabled. Note that the patch does not make the setting of the sysfs variable "disable" coherent, i.e. if one is disabling a light state, then all deeper states are disabled as well, but the "disable" variable does not reflect it. Likewise, if one enables a deep state but a lighter state still is disabled, then this has no effect. A related section has been added to the documentation. Signed-off-by: Carsten Emde <C.Emde@osadl.org> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Diffstat (limited to 'drivers/cpuidle')
-rw-r--r--drivers/cpuidle/governors/ladder.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c
index b6a09ea859b..2aef26c520b 100644
--- a/drivers/cpuidle/governors/ladder.c
+++ b/drivers/cpuidle/governors/ladder.c
@@ -88,6 +88,7 @@ static int ladder_select_state(struct cpuidle_driver *drv,
88 88
89 /* consider promotion */ 89 /* consider promotion */
90 if (last_idx < drv->state_count - 1 && 90 if (last_idx < drv->state_count - 1 &&
91 !dev->states_usage[last_idx + 1].disable &&
91 last_residency > last_state->threshold.promotion_time && 92 last_residency > last_state->threshold.promotion_time &&
92 drv->states[last_idx + 1].exit_latency <= latency_req) { 93 drv->states[last_idx + 1].exit_latency <= latency_req) {
93 last_state->stats.promotion_count++; 94 last_state->stats.promotion_count++;
@@ -100,7 +101,8 @@ static int ladder_select_state(struct cpuidle_driver *drv,
100 101
101 /* consider demotion */ 102 /* consider demotion */
102 if (last_idx > CPUIDLE_DRIVER_STATE_START && 103 if (last_idx > CPUIDLE_DRIVER_STATE_START &&
103 drv->states[last_idx].exit_latency > latency_req) { 104 (dev->states_usage[last_idx].disable ||
105 drv->states[last_idx].exit_latency > latency_req)) {
104 int i; 106 int i;
105 107
106 for (i = last_idx - 1; i > CPUIDLE_DRIVER_STATE_START; i--) { 108 for (i = last_idx - 1; i > CPUIDLE_DRIVER_STATE_START; i--) {