On 04/02/2013 11:37 AM, jonghwa3.lee@xxxxxxxxxxx wrote: > On 2013년 04월 02일 16:34, Daniel Lezcano wrote: > >> On 04/02/2013 08:17 AM, jonghwa3.lee@xxxxxxxxxxx wrote: >>> On 2013년 04월 02일 14:00, Daniel Lezcano wrote: >>> >>>> On 04/01/2013 10:24 AM, Jonghwa Lee wrote: >>>>> This patch adds idle state time stamp to cpuidle device structure to >>>>> notify its current idle state. If last enter time is newer than last >>>>> exit time, then it means that the core is in idle now. >>>>> >>>>> Signed-off-by: Jonghwa Lee <jonghwa3.lee@xxxxxxxxxxx> >>>>> --- >>>> >>>> The patch description does not explain what problem you want to solve, >>>> how to solve it and the patch itself shows nothing. >>>> >>>> Could you elaborate ? >>> >>> >>> I'm sorry for lacking description. I supplement more. >>> >>> This patch does add time-stamp for idle enter/exit only nothing more. >>> The reason why I needed them is that I wanted to know current cpu idle >>> state. It is hard to know whether cpu is in idle or not now. >> >> Did you looked at: >> >> include/linux/sched.h:extern int idle_cpu(int cpu); >> > > > Yes, I did. > >> ? >> >>> When I check the cpuidle state usage, sometimes the information is wrong. >>> Because it is updated only when the cpu exits the idle state. So while the >>> cpu is idling, the cpuidle state usage holds past one. Therefore I put >>> the time-stamp for cpuidle enter/exit for checking current idling and >>> calculating idle state usage correctly. >>> >>> I just make this patch temporary for my cpufreq governor work. So, it just >>> use time-stamp for all idle state together. After RFC working, I have a plan >>> to update this patch to use timestamp for each idle state. >> >> I suggest you look at the enter_idle / exit_idle function and make your >> governor to subscribe to the IDLE_START/EXIT notifiers. >> >> arch/x86/kernel/process.c >> >> These are defined for the x86 architecture, maybe worth to add it to >> another architecture. >> > > > Thanks for your opinion. > > Actually, I work on ARM architecture and I knew that the attempt of applying > idle notifier was failed. You probably knew it, because the link you gave me > before is that attempt. (https://lkml.org/lkml/2012/2/7/504) :) Yeah, now I recall this thread. > Currently, there > is only notifying call which is for led in arch/arm/kernel/process.c and I think > it isn't for me to use. Anyway, Do you really think it is better way to use > notifier than my way? Because I think it is too heavy for me. On my board, > sometimes entering idle happened hundreds times during the 100ms. I don't want > to call notifier that much time. IMO, just moving local variable to per-cpu > variable for showing the enter/exit time looks better although it requires code > modification on cpudile side. What do you think? Sorry, but it is hard to figure out what you are trying to achieve with a single patch. IIUC, you want to know how long the cpu is idle including the current state, right ? So you need to know if the cpu is idle and when it entered the idle state, correct ? If the cpu is idle and the information is per cpu, how will you read this value from another cpu without introducing a locking mechanism ? Does it mean the cpufreq governor needs cpuidle ? I am wondering if these informations shouldn't be retrieved from the scheduler, not from cpuidle. -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
