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

Masami Hiramatsu
2023-10-29T02:54:58Z

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?
>
> >
> > 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

--
Masami Hiramatsu (Google) <mhiramat@kernel.org>