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cpuidle: add a sysfs entry to disable specific C state for debug purp…

…ose.

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 <shuox.liu@intel.com>
Reviewed-by: Yanmin Zhang <yanmin_zhang@intel.com>
Reviewed-and-Tested-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>
  • Loading branch information...
commit 3a53396b0381ec9d5180fd8fe7a681c8ce95fd9a 1 parent 6a6ea0a
ShuoX Liu authored lenb committed
5 Documentation/cpuidle/sysfs.txt
View
@@ -36,6 +36,7 @@ drwxr-xr-x 2 root root 0 Feb 8 10:42 state3
/sys/devices/system/cpu/cpu0/cpuidle/state0:
total 0
-r--r--r-- 1 root root 4096 Feb 8 10:42 desc
+-rw-r--r-- 1 root root 4096 Feb 8 10:42 disable
-r--r--r-- 1 root root 4096 Feb 8 10:42 latency
-r--r--r-- 1 root root 4096 Feb 8 10:42 name
-r--r--r-- 1 root root 4096 Feb 8 10:42 power
@@ -45,6 +46,7 @@ total 0
/sys/devices/system/cpu/cpu0/cpuidle/state1:
total 0
-r--r--r-- 1 root root 4096 Feb 8 10:42 desc
+-rw-r--r-- 1 root root 4096 Feb 8 10:42 disable
-r--r--r-- 1 root root 4096 Feb 8 10:42 latency
-r--r--r-- 1 root root 4096 Feb 8 10:42 name
-r--r--r-- 1 root root 4096 Feb 8 10:42 power
@@ -54,6 +56,7 @@ total 0
/sys/devices/system/cpu/cpu0/cpuidle/state2:
total 0
-r--r--r-- 1 root root 4096 Feb 8 10:42 desc
+-rw-r--r-- 1 root root 4096 Feb 8 10:42 disable
-r--r--r-- 1 root root 4096 Feb 8 10:42 latency
-r--r--r-- 1 root root 4096 Feb 8 10:42 name
-r--r--r-- 1 root root 4096 Feb 8 10:42 power
@@ -63,6 +66,7 @@ total 0
/sys/devices/system/cpu/cpu0/cpuidle/state3:
total 0
-r--r--r-- 1 root root 4096 Feb 8 10:42 desc
+-rw-r--r-- 1 root root 4096 Feb 8 10:42 disable
-r--r--r-- 1 root root 4096 Feb 8 10:42 latency
-r--r--r-- 1 root root 4096 Feb 8 10:42 name
-r--r--r-- 1 root root 4096 Feb 8 10:42 power
@@ -72,6 +76,7 @@ total 0
* desc : Small description about the idle state (string)
+* disable : Option to disable this idle state (bool)
* latency : Latency to exit out of this idle state (in microseconds)
* name : Name of the idle state (string)
* power : Power consumed while in this idle state (in milliwatts)
1  drivers/cpuidle/cpuidle.c
View
@@ -245,6 +245,7 @@ static void poll_idle_init(struct cpuidle_driver *drv)
state->power_usage = -1;
state->flags = 0;
state->enter = poll_idle;
+ state->disable = 0;
}
#else
static void poll_idle_init(struct cpuidle_driver *drv) {}
5 drivers/cpuidle/governors/menu.c
View
@@ -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)
40 drivers/cpuidle/sysfs.c
View
@@ -11,6 +11,7 @@
#include <linux/sysfs.h>
#include <linux/slab.h>
#include <linux/cpu.h>
+#include <linux/capability.h>
#include "cpuidle.h"
@@ -222,6 +223,9 @@ struct cpuidle_state_attr {
#define define_one_state_ro(_name, show) \
static struct cpuidle_state_attr attr_##_name = __ATTR(_name, 0444, show, NULL)
+#define define_one_state_rw(_name, show, store) \
+static struct cpuidle_state_attr attr_##_name = __ATTR(_name, 0644, show, store)
+
#define define_show_state_function(_name) \
static ssize_t show_state_##_name(struct cpuidle_state *state, \
struct cpuidle_state_usage *state_usage, char *buf) \
@@ -229,6 +233,24 @@ static ssize_t show_state_##_name(struct cpuidle_state *state, \
return sprintf(buf, "%u\n", state->_name);\
}
+#define define_store_state_function(_name) \
+static ssize_t store_state_##_name(struct cpuidle_state *state, \
+ const char *buf, size_t size) \
+{ \
+ long value; \
+ int err; \
+ if (!capable(CAP_SYS_ADMIN)) \
+ return -EPERM; \
+ err = kstrtol(buf, 0, &value); \
+ if (err) \
+ return err; \
+ if (value) \
+ state->disable = 1; \
+ else \
+ state->disable = 0; \
+ return size; \
+}
+
#define define_show_state_ull_function(_name) \
static ssize_t show_state_##_name(struct cpuidle_state *state, \
struct cpuidle_state_usage *state_usage, char *buf) \
@@ -251,6 +273,8 @@ define_show_state_ull_function(usage)
define_show_state_ull_function(time)
define_show_state_str_function(name)
define_show_state_str_function(desc)
+define_show_state_function(disable)
+define_store_state_function(disable)
define_one_state_ro(name, show_state_name);
define_one_state_ro(desc, show_state_desc);
@@ -258,6 +282,7 @@ define_one_state_ro(latency, show_state_exit_latency);
define_one_state_ro(power, show_state_power_usage);
define_one_state_ro(usage, show_state_usage);
define_one_state_ro(time, show_state_time);
+define_one_state_rw(disable, show_state_disable, store_state_disable);
static struct attribute *cpuidle_state_default_attrs[] = {
&attr_name.attr,
@@ -266,6 +291,7 @@ static struct attribute *cpuidle_state_default_attrs[] = {
&attr_power.attr,
&attr_usage.attr,
&attr_time.attr,
+ &attr_disable.attr,
NULL
};
@@ -287,8 +313,22 @@ static ssize_t cpuidle_state_show(struct kobject * kobj,
return ret;
}
+static ssize_t cpuidle_state_store(struct kobject *kobj,
+ struct attribute *attr, const char *buf, size_t size)
+{
+ int ret = -EIO;
+ struct cpuidle_state *state = kobj_to_state(kobj);
+ struct cpuidle_state_attr *cattr = attr_to_stateattr(attr);
+
+ if (cattr->store)
+ ret = cattr->store(state, buf, size);
+
+ return ret;
+}
+
static const struct sysfs_ops cpuidle_state_sysfs_ops = {
.show = cpuidle_state_show,
+ .store = cpuidle_state_store,
};
static void cpuidle_state_sysfs_release(struct kobject *kobj)
1  include/linux/cpuidle.h
View
@@ -46,6 +46,7 @@ struct cpuidle_state {
unsigned int exit_latency; /* in US */
unsigned int power_usage; /* in mW */
unsigned int target_residency; /* in US */
+ unsigned int disable;
int (*enter) (struct cpuidle_device *dev,
struct cpuidle_driver *drv,
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