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    SubjectRe: Subject: [PATCH] cpuidle: Add a sysfs entry to disable specific C state for debug purpose.
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    Date
    On Wed, 2012-02-29 at 04:55 +0000, Liu, ShuoX wrote:
    > From: ShuoX Liu <shuox.liu@intel.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.
    >
    > Signed-off-by: ShuoX Liu <shuox.liu@intel.com>
    Andrew,

    Would you like to merge the patch into your testing tree? It's useful to help
    developers debug some issues.

    Thanks,
    Yanmin

    > ---
    > drivers/cpuidle/cpuidle.c | 1 +
    > drivers/cpuidle/governors/menu.c | 5 ++++-
    > drivers/cpuidle/sysfs.c | 34 ++++++++++++++++++++++++++++++++++
    > include/linux/cpuidle.h | 1 +
    > 4 files changed, 40 insertions(+), 1 deletions(-)
    >
    > 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,




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