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

Randy Dunlap
2023-10-28T16:48:47Z

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...

> + clock.
> +
> What: /sys/power/sync_on_suspend
> Date: October 2019
> Contact: Jonas Meurer <jonas@freesources.org>

[snip]

Thanks.
--
~Randy