From 3a53396b0381ec9d5180fd8fe7a681c8ce95fd9a Mon Sep 17 00:00:00 2001 From: ShuoX Liu Date: Wed, 28 Mar 2012 15:19:11 -0700 Subject: cpuidle: add a sysfs entry to disable specific C state for debug purpose. Some C states of new CPU might be not good. One reason is BIOS might configure them incorrectly. To help developers root cause it quickly, the patch adds a new sysfs entry, so developers could disable specific C state manually. In addition, C state might have much impact on performance tuning, as it takes much time to enter/exit C states, which might delay interrupt processing. With the new debug option, developers could check if a deep C state could impact performance and how much impact it could cause. Also add this option in Documentation/cpuidle/sysfs.txt. [akpm@linux-foundation.org: check kstrtol return value] Signed-off-by: ShuoX Liu Reviewed-by: Yanmin Zhang Reviewed-and-Tested-by: Deepthi Dharwar Signed-off-by: Andrew Morton Signed-off-by: Len Brown --- drivers/cpuidle/governors/menu.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'drivers/cpuidle/governors') diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index ad0952601ae2..5c17ca112fc2 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -280,7 +280,8 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) * We want to default to C1 (hlt), not to busy polling * unless the timer is happening really really soon. */ - if (data->expected_us > 5) + if (data->expected_us > 5 && + drv->states[CPUIDLE_DRIVER_STATE_START].disable == 0) data->last_state_idx = CPUIDLE_DRIVER_STATE_START; /* @@ -290,6 +291,8 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++) { struct cpuidle_state *s = &drv->states[i]; + if (s->disable) + continue; if (s->target_residency > data->predicted_us) continue; if (s->exit_latency > latency_req) -- cgit v1.2.3