Messages in this thread | | | Date | Fri, 1 Feb 2013 10:56:05 +0900 | From | Yasuaki Ishimatsu <> | Subject | Re: [PATCH V3] suspend: enable freeze timeout configuration through sys |
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2013/02/01 10:33, Li, Fei wrote: >> -----Original Message----- >> From: Rafael J. Wysocki [mailto:rjw@sisk.pl] >> Sent: Friday, February 01, 2013 6:29 AM >> To: anish singh; Li, Fei >> Cc: Yasuaki Ishimatsu; akpm@linux-foundation.org; linux-kernel@vger.kernel.org; >> linux-pm@vger.kernel.org; Liu, Chuansheng >> Subject: Re: [PATCH V3] suspend: enable freeze timeout configuration through >> sys >> >> On Thursday, January 31, 2013 03:22:25 PM anish singh wrote: >>> On Thu, Jan 31, 2013 at 2:43 PM, Li, Fei <fei.li@intel.com> wrote: >>>>> -----Original Message----- >>>>> From: Yasuaki Ishimatsu [mailto:isimatu.yasuaki@jp.fujitsu.com] >>>>> Sent: Thursday, January 31, 2013 3:30 PM >>>>> To: Li, Fei >>>>> Cc: rjw@sisk.pl; akpm@linux-foundation.org; linux-kernel@vger.kernel.org; >>>>> linux-pm@vger.kernel.org; Liu, Chuansheng >>>>> Subject: Re: [PATCH V3] suspend: enable freeze timeout configuration >> through >>>>> sys >>>>> >>>>> 2013/01/31 13:55, fli24 wrote: >>>>>> >>>>>> At present, the value of timeout for freezing is 20s, which is >>>>>> meaningless in case that one thread is frozen with mutex locked >>>>>> and another thread is trying to lock the mutex, as this time of >>>>>> freezing will fail unavoidably. >>>>>> And if there is no new wakeup event registered, the system will >>>>>> waste at most 20s for such meaningless trying of freezing. >>>>>> >>>>>> With this patch, the value of timeout can be configured to smaller >>>>>> value, so such meaningless trying of freezing will be aborted in >>>>>> earlier time, and later freezing can be also triggered in earlier >>>>>> time. And more power will be saved. >>>>>> In normal case on mobile phone, it costs real little time to freeze >>>>>> processes. On some platform, it only costs about 20ms to freeze >>>>>> user space processes and 10ms to freeze kernel freezable threads. >>>>>> >>>>>> Signed-off-by: Liu Chuansheng <chuansheng.liu@intel.com> >>>>>> Signed-off-by: Li Fei <fei.li@intel.com> >>>>>> --- >>>>>> Documentation/power/freezing-of-tasks.txt | 5 +++++ >>>>>> include/linux/freezer.h | 5 +++++ >>>>>> kernel/power/main.c | 27 >>>>> +++++++++++++++++++++++++++ >>>>>> kernel/power/process.c | 4 ++-- >>>>>> 4 files changed, 39 insertions(+), 2 deletions(-) >>>>>> >>>>>> diff --git a/Documentation/power/freezing-of-tasks.txt >>>>> b/Documentation/power/freezing-of-tasks.txt >>>>>> index 6ec291e..85894d8 100644 >>>>>> --- a/Documentation/power/freezing-of-tasks.txt >>>>>> +++ b/Documentation/power/freezing-of-tasks.txt >>>>>> @@ -223,3 +223,8 @@ since they ask the freezer to skip freezing this >> task, >>>>> since it is anyway >>>>>> only after the entire suspend/hibernation sequence is complete. >>>>>> So, to summarize, use [un]lock_system_sleep() instead of directly using >>>>>> mutex_[un]lock(&pm_mutex). That would prevent freezing failures. >>>>>> + >>>>>> +V. Miscellaneous >>>>>> +/sys/power/pm_freeze_timeout controls how long it will cost at most to >>>>> freeze >>>>>> +all user space processes or all freezable kernel threads, in unit of >> millisecond. >>>>>> +The default value is 20000, with range of unsigned integer. >>>>>> diff --git a/include/linux/freezer.h b/include/linux/freezer.h >>>>>> index e4238ce..5a24a33 100644 >>>>>> --- a/include/linux/freezer.h >>>>>> +++ b/include/linux/freezer.h >>>>>> @@ -13,6 +13,11 @@ extern bool pm_freezing; /* PM >> freezing in effect >>>>> */ >>>>>> extern bool pm_nosig_freezing; /* PM nosig freezing in >> effect */ >>>>>> >>>>>> /* >>>>>> + * Timeout for stopping processes >>>>>> + */ >>>>>> +extern unsigned int sys_freeze_process_timeout_msecs; >>>>>> + >>>>>> +/* >>>>>> * Check if a process has been frozen >>>>>> */ >>>>>> static inline bool frozen(struct task_struct *p) >>>>>> diff --git a/kernel/power/main.c b/kernel/power/main.c >>>>>> index 1c16f91..453ead1 100644 >>>>>> --- a/kernel/power/main.c >>>>>> +++ b/kernel/power/main.c >>>>>> @@ -553,6 +553,30 @@ power_attr(pm_trace_dev_match); >>>>>> >>>>>> #endif /* CONFIG_PM_TRACE */ >>>>>> >>>>>> +#ifdef CONFIG_FREEZER >>>>>> +static ssize_t pm_freeze_timeout_show(struct kobject *kobj, >>>>>> + struct kobj_attribute *attr, char >> *buf) >>>>>> +{ >>>>>> + return sprintf(buf, "%u\n", sys_freeze_process_timeout_msecs); >>>>>> +} >>>>>> + >>>>>> +static ssize_t pm_freeze_timeout_store(struct kobject *kobj, >>>>>> + struct kobj_attribute *attr, >>>>>> + const char *buf, size_t n) >>>>>> +{ >>>>>> + unsigned long val; >>>>>> + >>>>>> + if (kstrtoul(buf, 10, &val)) >>>>>> + return -EINVAL; >>>>>> + >>>>>> + sys_freeze_process_timeout_msecs = val; >>>>>> + return n; >>>>>> +} >>>>>> + >>>>>> +power_attr(pm_freeze_timeout); >>>>>> + >>>>>> +#endif /* CONFIG_FREEZER*/ >>>>>> + >>>>>> static struct attribute * g[] = { >>>>>> &state_attr.attr, >>>>>> #ifdef CONFIG_PM_TRACE >>>>>> @@ -576,6 +600,9 @@ static struct attribute * g[] = { >>>>>> &pm_print_times_attr.attr, >>>>>> #endif >>>>>> #endif >>>>>> +#ifdef CONFIG_FREEZER >>>>>> + &pm_freeze_timeout_attr.attr, >>>>>> +#endif >>>>>> NULL, >>>>>> }; >>>>>> >>>>>> diff --git a/kernel/power/process.c b/kernel/power/process.c >>>>>> index d5a258b..ba45a26 100644 >>>>>> --- a/kernel/power/process.c >>>>>> +++ b/kernel/power/process.c >>>>>> @@ -21,7 +21,7 @@ >>>>>> /* >>>>>> * Timeout for stopping processes >>>>>> */ >>>>> >>>>>> -#define TIMEOUT (20 * HZ) >>>>>> +unsigned int __read_mostly sys_freeze_process_timeout_msecs = >> 20000; >>>>> >>>>> 20000 does not mean 20 seconds since we can select HZ other than 1000. >>>>> So (20 * HZ) is better than 20000. >>>>> >>>> [Li, Fei] >>>> Are you sure about this, (20*HZ) better than 20000, or you mean 20 * >> MSEC_PER_SEC? >>> Yasuaki mean HZ value will not always be 1000.The value of HZ differs for >> each >>> supported architecture. In fact, on some supported architectures, >>> it even differs between machine types. >>> When writing kernel code, never assume that HZ has any given value. >>> Right now you are assuming that the delay will be always 20 seconds because >> of >>> your assumption of HZ. >> >> That's correct, the initial value should be 20 * HZ (i.e. as before). > [Li, Fei] > Yes, you are right, and IMHO it's already as this in the patch, > as 20 * HZ == msecs_to_jiffies(20000), with the current definition MSEC_PER_SEC > of 1000L. I'll update the default value as 20 * MSEC_PER_SEC in patch V4.
20 * MSEC_PER_SEC is not 20 seconds. In Linux, 1 * HZ is 1 seconds. Thus, - If HZ is defined as 1000, 1000 is 1 seconds. - If HZ is defined as 250, 250 is 1 seconds.
20 * MSEC_PER_SEC is always 20000. Thus, - If HZ is defined as 1000, 20 * MSEC_PER_SEC is 20 seconds. - If HZ is defined as 250, 20 * MSEC_PER_SEC is 80 seconds.
So you should use 20 * HZ if you define timeout at 20 seconds.
Thanks, Yasuaki Ishimatsu.
> >> Besides, the name of the variable doesn't need to be _that_ long. >> What about freeze_timeout_msecs? > [Li, Fei] > Agree with you, and will update it in patch V4. > > Thanks and Regards, > Li Fei > >> Rafael >> >> >> -- >> I speak only for myself. >> Rafael J. Wysocki, Intel Open Source Technology Center.
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