| Message ID | 5006CA64.4070003@osadl.org (mailing list archive) |
|---|---|
| State | Changes Requested, archived |
| Headers | show |
On 07/18/2012 08:08 PM, Carsten Emde wrote: > On 07/18/2012 01:48 PM, Deepthi Dharwar wrote: >> On 07/18/2012 04:32 PM, Carsten Emde wrote: >>> On 07/18/2012 08:36 AM, Deepthi Dharwar wrote: >>>> On 07/18/2012 12:29 AM, Carsten Emde wrote: >>>>> 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. >>>> >>>> Yes, I agree that currently that disabling a particular C-state >>>> is not reflected in working of ladder governor. This patch is needed >>>> to fix it on ladder too. >>>> >>>> Also wanted to clarify on the intended implementation here, >>>> if there are say 5 C-states on a system, disabling 2nd >>>> state would also end by disabling all the remaining 3 deeper states too >>>> as ladder governor enters the lightest state first, and will only move >>>> on to the next deeper state if a idle period was long enough as >>>> per the implementation. >>>> If one is disabling only the deepest state, then it would >>>> work as intended. >>> Yes, 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. >> >> Agree, as per the ladder design. >> >>> I could implement a sanitize mechanism of the ladder governor that >>> takes care the "disable" variables of all deeper states are set to 1, >>> if a state is disabled, and those of all lighter states are set to 0, >>> if a state is enabled. Do you wish me to do that? >> >> No, I dont think thats necessary, current code suffices it. >> The disable flag is knob we are giving to the user . So may be just >> document the intended use of disable flag working >> alongside design of ladder governor. > It's not necessary - but maybe better. Here comes v3 with a sanitizer. > Is this too ugly? > The v2, with the documentation in place seems sufficient. Yup, this adds unnecessary fields which are not much use coz the same can be achieved with just disable flag check. Also, any reason why the patch is being sent as an attachment ? Sending patches as an attachment is not a recommended practice. Cheers, Deepthi > -Carsten. > -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Deepthi, >>> [..] >>>> I could implement a sanitize mechanism of the ladder governor that >>>> takes care the "disable" variables of all deeper states are set to 1, >>>> if a state is disabled, and those of all lighter states are set to 0, >>>> if a state is enabled. Do you wish me to do that? >>> No, I dont think thats necessary, current code suffices it. >>> The disable flag is knob we are giving to the user . So may be just >>> document the intended use of disable flag working >>> alongside design of ladder governor. >> It's not necessary - but maybe better. Here comes v3 with a sanitizer. >> Is this too ugly? > The v2, with the documentation in place seems sufficient. > Yup, this adds unnecessary fields which are not much use > coz the same can be achieved with just disable flag check. ok, let's take v2. > Also, any reason why the patch is being sent as an attachment ? > Sending patches as an attachment is not a recommended practice. Sorry. -Carsten. -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi, On Thursday, July 19, 2012, Carsten Emde wrote: > Deepthi, > > >>> [..] > >>>> I could implement a sanitize mechanism of the ladder governor that > >>>> takes care the "disable" variables of all deeper states are set to 1, > >>>> if a state is disabled, and those of all lighter states are set to 0, > >>>> if a state is enabled. Do you wish me to do that? > >>> No, I dont think thats necessary, current code suffices it. > >>> The disable flag is knob we are giving to the user . So may be just > >>> document the intended use of disable flag working > >>> alongside design of ladder governor. > >> It's not necessary - but maybe better. Here comes v3 with a sanitizer. > >> Is this too ugly? > > The v2, with the documentation in place seems sufficient. > > Yup, this adds unnecessary fields which are not much use > > coz the same can be achieved with just disable flag check. > ok, let's take v2. > > > Also, any reason why the patch is being sent as an attachment ? > > Sending patches as an attachment is not a recommended practice. > Sorry. Can you please resend the version regarded as the current one? And please send it inline this time. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Rafael, >>>>>> [..] >>>>>> I could implement a sanitize mechanism of the ladder governor that >>>>>> takes care the "disable" variables of all deeper states are set to 1, >>>>>> if a state is disabled, and those of all lighter states are set to 0, >>>>>> if a state is enabled. Do you wish me to do that? >>>>> No, I dont think thats necessary, current code suffices it. >>>>> The disable flag is knob we are giving to the user . So may be just >>>>> document the intended use of disable flag working >>>>> alongside design of ladder governor. >>>> It's not necessary - but maybe better. Here comes v3 with a sanitizer. >>>> Is this too ugly? >>> The v2, with the documentation in place seems sufficient. >>> Yup, this adds unnecessary fields which are not much use >>> coz the same can be achieved with just disable flag check. >> ok, let's take v2. > Can you please resend the version regarded as the current one? This is the version that was regarded as the current one (v2). Changes in v2: A note in the documentation explains why the sysfs variable "disable" may not always reflect the current situation and why modifying it may not always work as expected. -Carsten. -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Carsten Emde <C.Emde@osadl.org> Subject: 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. A sanitize mechanism takes care the disable variables of all deeper states are set to 1, if a state is disabled, and those of all lighter states are set to 0, if a state is enabled. Signed-off-by: Carsten Emde <C.Emde@osadl.org> --- drivers/cpuidle/governors/ladder.c | 25 ++++++++++++++++++++++++- drivers/cpuidle/sysfs.c | 6 ++++++ include/linux/cpuidle.h | 4 ++++ 3 files changed, 34 insertions(+), 1 deletion(-) Index: linux-3.4.4-rt14-rc2-64/drivers/cpuidle/governors/ladder.c =================================================================== --- linux-3.4.4-rt14-rc2-64.orig/drivers/cpuidle/governors/ladder.c +++ linux-3.4.4-rt14-rc2-64/drivers/cpuidle/governors/ladder.c @@ -58,6 +58,25 @@ static inline void ladder_do_selection(s ldev->last_state_idx = new_idx; } +void notify_state_modified(struct cpuidle_state *state) +{ + if (state->disable) { + /* synchronize all deeper states, if any */ + int states = state->state_count - 1 - state->state_no; + struct cpuidle_state *last = state + states; + + while (++state <= last) + state->disable = 1; + } else { + /* synchronize all lighter states, if any */ + int states = state->state_no; + struct cpuidle_state *first = state - states; + + while (--state >= first) + state->disable = 0; + } +} + /** * ladder_select_state - selects the next state to enter * @drv: cpuidle driver @@ -88,6 +107,7 @@ static int ladder_select_state(struct cp /* consider promotion */ if (last_idx < drv->state_count - 1 && + !drv->states[last_idx + 1].disable && last_residency > last_state->threshold.promotion_time && drv->states[last_idx + 1].exit_latency <= latency_req) { last_state->stats.promotion_count++; @@ -100,7 +120,8 @@ static int ladder_select_state(struct cp /* consider demotion */ if (last_idx > CPUIDLE_DRIVER_STATE_START && - drv->states[last_idx].exit_latency > latency_req) { + (drv->states[last_idx].disable || + drv->states[last_idx].exit_latency > latency_req)) { int i; for (i = last_idx - 1; i > CPUIDLE_DRIVER_STATE_START; i--) { @@ -154,6 +175,8 @@ static int ladder_enable_device(struct c lstate->threshold.promotion_time = state->exit_latency; if (i > 0) lstate->threshold.demotion_time = state->exit_latency; + + state->notify = notify_state_modified; } return 0; Index: linux-3.4.4-rt14-rc2-64/drivers/cpuidle/sysfs.c =================================================================== --- linux-3.4.4-rt14-rc2-64.orig/drivers/cpuidle/sysfs.c +++ linux-3.4.4-rt14-rc2-64/drivers/cpuidle/sysfs.c @@ -239,15 +239,19 @@ static ssize_t store_state_##_name(struc { \ long value; \ int err; \ + unsigned int old; \ if (!capable(CAP_SYS_ADMIN)) \ return -EPERM; \ err = kstrtol(buf, 0, &value); \ if (err) \ return err; \ + old = state->disable; \ if (value) \ state->disable = 1; \ else \ state->disable = 0; \ + if (state->notify && state->disable != old) \ + state->notify(state); \ return size; \ } @@ -377,6 +381,8 @@ int cpuidle_add_state_sysfs(struct cpuid kfree(kobj); goto error_state; } + drv->states[i].state_no = i; + drv->states[i].state_count = device->state_count; kobject_uevent(&kobj->kobj, KOBJ_ADD); device->kobjs[i] = kobj; } Index: linux-3.4.4-rt14-rc2-64/include/linux/cpuidle.h =================================================================== --- linux-3.4.4-rt14-rc2-64.orig/include/linux/cpuidle.h +++ linux-3.4.4-rt14-rc2-64/include/linux/cpuidle.h @@ -47,6 +47,10 @@ struct cpuidle_state { int power_usage; /* in mW */ unsigned int target_residency; /* in US */ unsigned int disable; + unsigned int state_no; + unsigned int state_count; + + void (*notify) (struct cpuidle_state *state); int (*enter) (struct cpuidle_device *dev, struct cpuidle_driver *drv,