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Message-ID: <4F545A4E.8010801@linux.vnet.ibm.com>
Date: Mon, 05 Mar 2012 11:46:46 +0530
From: Deepthi Dharwar <deepthi@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
"yanmin_zhang@...ux.intel.com" <yanmin_zhang@...ux.intel.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Brown, Len" <len.brown@...el.com>, Ingo Molnar <mingo@...e.hu>,
Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>,
linux-pm@...ts.linux-foundation.org
Subject: Re: Subject: [PATCH] cpuidle: Add a sysfs entry to disable specific
C state for debug purpose.
Hi,
On 03/05/2012 08:52 AM, Liu, ShuoX wrote:
>>> It's useful to help developers debug some issues.
>>
>> It would help developers more if it was documented a bit. As it
>> stands, they'd be lucky if they even knew it existed.
>>
>> Looky:
>>
>> akpm:/usr/src/linux-3.3-rc5> grep -ril cpuidle Documentation
>> Documentation/trace/events-power.txt
>> Documentation/ABI/testing/sysfs-devices-system-cpu
>> Documentation/kernel-parameters.txt
>> Documentation/00-INDEX
>> Documentation/cpuidle/core.txt
>> Documentation/cpuidle/sysfs.txt
>> Documentation/cpuidle/driver.txt
>> Documentation/cpuidle/governor.txt
>
> Thanks Andrew's advice and Yanmin's review. Here is the new patch.
>
> From: ShuoX Liu <shuox.liu@...el.com>
>
> 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.
Enabling/Disabling particular C-states from sysfs entry is really
helpful for cpuidle developers for general debugging and performance
tuning for not just x86 but for all platforms that support cpuidle,
like arm, powerpc etc .
>
> Signed-off-by: ShuoX Liu <shuox.liu@...el.com>
> Reviewed-by: Yanmin Zhang <yanmin_zhang@...ux.intel.com>
> ---
> Documentation/cpuidle/sysfs.txt | 5 +++++
> drivers/cpuidle/cpuidle.c | 1 +
> drivers/cpuidle/governors/menu.c | 5 ++++-
> drivers/cpuidle/sysfs.c | 34 ++++++++++++++++++++++++++++++++++
> include/linux/cpuidle.h | 1 +
> 5 files changed, 45 insertions(+), 1 deletions(-)
>
> diff --git a/Documentation/cpuidle/sysfs.txt b/Documentation/cpuidle/sysfs.txt
> index 50d7b16..635424f 100644
> --- a/Documentation/cpuidle/sysfs.txt
> +++ b/Documentation/cpuidle/sysfs.txt
> @@ -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
> +-r--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
Please update the documentation, rw fields are valid
for disable flag
/sys/devices/system/cpu/cpu2/cpuidle/state1 # ls -l
total 0
-r--r--r-- 1 root root 65536 Mar 5 11:28 desc
-rw-r--r-- 1 root root 65536 Mar 5 11:28 disable
-r--r--r-- 1 root root 65536 Mar 5 11:28 latency
-r--r--r-- 1 root root 65536 Mar 5 11:28 name
-r--r--r-- 1 root root 65536 Mar 5 11:28 power
-r--r--r-- 1 root root 65536 Mar 5 11:28 time
-r--r--r-- 1 root root 65536 Mar 5 11:28 usage
> @@ -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
> +-r--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
> +-r--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
> +-r--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)
> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> index 59f4261..7d66d3e 100644
> --- a/drivers/cpuidle/cpuidle.c
> +++ b/drivers/cpuidle/cpuidle.c
> @@ -197,6 +197,7 @@ 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) {}
> diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
> index ad09526..5c17ca1 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)
> diff --git a/drivers/cpuidle/sysfs.c b/drivers/cpuidle/sysfs.c
> index 3fe41fe..1eae29a 100644
> --- a/drivers/cpuidle/sysfs.c
> +++ b/drivers/cpuidle/sysfs.c
> @@ -222,6 +222,9 @@ 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 +232,19 @@ 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) \
> +{ \
> + int value; \
> + sscanf(buf, "%d", &value); \
> + 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 +267,8 @@ 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 +276,7 @@ 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 +285,7 @@ static struct attribute *cpuidle_state_default_attrs[] = {
> &attr_power.attr,
> &attr_usage.attr,
> &attr_time.attr,
> + &attr_disable.attr,
> NULL
> };
>
> @@ -287,8 +307,22 @@ 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)
> diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
> index 712abcc..eb150a5 100644
> --- a/include/linux/cpuidle.h
> +++ b/include/linux/cpuidle.h
> @@ -45,6 +45,7 @@ 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,
>
Reviewed-and-Tested-by: Deepthi Dharwar <deepthi@...ux.vnet.ibm.com>
Cheers,
Deepthi
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