Hi,

Here is the 8th version of the patch to expose last succeeded resumed
timestamp in sysfs as /sys/power/suspend_stats/last_success_resume_time.
The previous version is here.

https://lore.kernel.org/lkml/170359668692.1864392.6909734045167510522.stgit@mhiramat.roam.corp.google.com/

This version is just update against for the upstream kernel.


On some system like the ChromeOS, the system suspend and resume are
controlled by a power management process. The user-space tasks will be
noticed the suspend and the resume signal from it.
To improve the suspend/resume performance and/or to find regressions,
we would like to know how long the resume processes are taken in kernel
and in user-space.

This patch introduces a last succeeded resumed timestamp (just before
thawing processes) on sysfs which allows us to find when the kernel
resume process successfully done in MONOTONIC clock. Thus user processes
can measure the elapsed time taken by its resume process at any point
in time.

This will help us to detect abnormal value (longer time) process in
the resuming and quickly decide the root cause is in the kernel or
user-space. The kernel side we can use many tools (e.g. printk or
ftrace) but for user-space we need to define the starting point of
the resuming process. Actually, the kernel side needs to use local
clock because the clock subsystem is also suspended. But in that
case, user space can not use that timestamp because the local clock
is not exposed.

So this will be used something like

where_the_user_space_resume_finish() {
	clock_gettime(CLOCK_MONOTONIC, &etime_ts);
	fileread("/sys/.../last_success_resume_time", stime);
	convert_timespec(stime, &stime_ts);
	user_resume_time = timespec_delta(&etime_ts, &stime_ts);
	...
}

Thank you,

---

Masami Hiramatsu (1):
      PM: sleep: Expose last succeeded resumed timestamp in sysfs


 Documentation/ABI/testing/sysfs-power |   11 +++++++++++
 kernel/power/main.c                   |   28 ++++++++++++++++++++++++++++
 kernel/power/power.h                  |    1 +
 kernel/power/suspend.c                |    1 +
 4 files changed, 41 insertions(+)

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

Hi Rafael,

Gentry ping. I would like to hear your comment on it.

Thank you,

On Tue,  2 Jul 2024 23:24:43 +0900
"Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:

> Hi,
> 
> Here is the 8th version of the patch to expose last succeeded resumed
> timestamp in sysfs as /sys/power/suspend_stats/last_success_resume_time.
> The previous version is here.
> 
> https://lore.kernel.org/lkml/170359668692.1864392.6909734045167510522.stgit@mhiramat.roam.corp.google.com/
> 
> This version is just update against for the upstream kernel.
> 
> 
> On some system like the ChromeOS, the system suspend and resume are
> controlled by a power management process. The user-space tasks will be
> noticed the suspend and the resume signal from it.
> To improve the suspend/resume performance and/or to find regressions,
> we would like to know how long the resume processes are taken in kernel
> and in user-space.
> 
> This patch introduces a last succeeded resumed timestamp (just before
> thawing processes) on sysfs which allows us to find when the kernel
> resume process successfully done in MONOTONIC clock. Thus user processes
> can measure the elapsed time taken by its resume process at any point
> in time.
> 
> This will help us to detect abnormal value (longer time) process in
> the resuming and quickly decide the root cause is in the kernel or
> user-space. The kernel side we can use many tools (e.g. printk or
> ftrace) but for user-space we need to define the starting point of
> the resuming process. Actually, the kernel side needs to use local
> clock because the clock subsystem is also suspended. But in that
> case, user space can not use that timestamp because the local clock
> is not exposed.
> 
> So this will be used something like
> 
> where_the_user_space_resume_finish() {
> 	clock_gettime(CLOCK_MONOTONIC, &etime_ts);
> 	fileread("/sys/.../last_success_resume_time", stime);
> 	convert_timespec(stime, &stime_ts);
> 	user_resume_time = timespec_delta(&etime_ts, &stime_ts);
> 	...
> }
> 
> Thank you,
> 
> ---
> 
> Masami Hiramatsu (1):
>       PM: sleep: Expose last succeeded resumed timestamp in sysfs
> 
> 
>  Documentation/ABI/testing/sysfs-power |   11 +++++++++++
>  kernel/power/main.c                   |   28 ++++++++++++++++++++++++++++
>  kernel/power/power.h                  |    1 +
>  kernel/power/suspend.c                |    1 +
>  4 files changed, 41 insertions(+)
> 
> --
> Masami Hiramatsu (Google) <mhiramat@kernel.org>


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