Re: [PATCH v3] PM: sleep: Expose last succeeded resumed timestamp in sysfs

Randy Dunlap
2023-10-29T12:17:01Z

Hi.

On 10/28/23 19:54, Masami Hiramatsu (Google) wrote:
> On Sat, 28 Oct 2023 09:48:36 -0700
> Randy Dunlap <rdunlap@infradead.org> wrote:
>
>> Hi,
>>
>> On 10/28/23 05:53, Masami Hiramatsu (Google) wrote:
>>> From: Masami Hiramatsu <mhiramat@kernel.org>
>>>
>>> Expose last succeeded resumed timestamp as last_success_resume_time
>>> attribute of suspend_stats in sysfs. This timestamp is recorded in
>>> CLOCK_MONOTONIC. So user can find the actual resumed time and
>>> measure the elapsed time from the time when the kernel finished
>>> the resume to the user-space action (e.g. display the UI).
>>
>> Can you go into the use-case a bit more, please?
>> You have said "what", but not "why".
>> What do you (or google) plan to do with this?

and what about this part of my questions? ^^^^^^^^^

>>
>>>
>>> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>>> ---
>>> Changes in v3:
>>> - Add (unsigned long long) casting for %llu.
>>> - Add a line after last_success_resume_time_show().
>>> Changes in v2:
>>> - Use %llu instead of %lu for printing u64 value.
>>> - Remove unneeded indent spaces from the last_success_resume_time
>>> line in the debugfs suspend_stat file.
>>> ---
>>> Documentation/ABI/testing/sysfs-power | 10 ++++++++++
>>> include/linux/suspend.h | 2 ++
>>> kernel/power/main.c | 15 +++++++++++++++
>>> kernel/power/suspend.c | 1 +
>>> 4 files changed, 28 insertions(+)
>>>
>>> diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
>>> index a3942b1036e2..63659765dee1 100644
>>> --- a/Documentation/ABI/testing/sysfs-power
>>> +++ b/Documentation/ABI/testing/sysfs-power
>>> @@ -442,6 +442,16 @@ Description:
>>> 'total_hw_sleep' and 'last_hw_sleep' may not be accurate.
>>> This number is measured in microseconds.
>>>
>>> +What: /sys/power/suspend_stats/last_success_resume_time
>>> +Date: Oct 2023
>>> +Contact: Masami Hiramatsu <mhiramat@kernel.org>
>>> +Description:
>>> + The /sys/power/suspend_stats/last_success_resume_time file
>>> + contains the timestamp of when the kernel successfully
>>> + resumed from suspend/hibernate.
>>> + This floating number is measured in seconds by monotonic
>>
>> What does "floating" mean here? Not floating point...
>
> Oops, it should be "floating point number".
>
> Thank you!
>
>>
>>
>>> + clock.
>>> +
>>> What: /sys/power/sync_on_suspend
>>> Date: October 2019
>>> Contact: Jonas Meurer <jonas@freesources.org>
>>
>> [snip]
>>
>> Thanks.
>> --
>> ~Randy
>
>

--
~Randy