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Message-ID: <171993029390.95379.9256588060965749271.stgit@mhiramat.roam.corp.google.com>
Date: Tue, 2 Jul 2024 23:24:54 +0900
From: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To: "Rafael J . Wysocki" <rafael@...nel.org>,
Pavel Machek <pavel@....cz>,
Len Brown <len.brown@...el.com>,
Randy Dunlap <rdunlap@...radead.org>
Cc: suleiman@...gle.com,
briannorris@...gle.com,
Masami Hiramatsu <mhiramat@...nel.org>,
linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org
Subject: [PATCH v8] PM: sleep: Expose last succeeded resumed timestamp in sysfs
From: Masami Hiramatsu <mhiramat@...nel.org>
Expose last succeeded resumed timestamp as last_success_resume_time
attribute of suspend_stats in sysfs so that user can use this time
stamp as a reference point of resuming user space.
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.
For this purpose, expose the accarate time when the kernel is finished
to resume so that we can distinguish the duration of kernel resume and
user space resume.
This suspend_stats attribute is easy to access and only expose the
timestamp in CLOCK_MONOTONIC. User can find the accarate time when the
kernel finished to resume its drivers/subsystems and start thawing, and
measure the elapsed time from the time when the kernel finished the
resume to a user-space action (e.g. displaying the UI).
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
---
Changes in v8:
- Update against the latest kernel.
- Introduce dpm_save_success_time() to update last_succeess_resume_time.
Changes in v7:
- Update patch description.
- Update sysfs documentation to say the exact timing.
- Update the comment.
Changes in v6:
- Fix to record resume time before thawing user processes.
Changes in v5:
- Just updated for v6.7-rc3.
Changes in v4.1:
- Fix document typo (again).
Changes in v4:
- Update description to add why.
- Fix document typo.
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 | 11 +++++++++++
kernel/power/main.c | 28 ++++++++++++++++++++++++++++
kernel/power/power.h | 1 +
kernel/power/suspend.c | 1 +
4 files changed, 41 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index a3942b1036e2..ee567e7e9d4a 100644
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -442,6 +442,17 @@ 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: Dec 2023
+Contact: Masami Hiramatsu <mhiramat@...nel.org>
+Description:
+ The /sys/power/suspend_stats/last_success_resume_time file
+ contains the timestamp of when the kernel successfully
+ resumed drivers/subsystems from suspend/hibernate. This is
+ just before thawing the user processes.
+ This floating point number is measured in seconds by monotonic
+ clock.
+
What: /sys/power/sync_on_suspend
Date: October 2019
Contact: Jonas Meurer <jonas@...esources.org>
diff --git a/kernel/power/main.c b/kernel/power/main.c
index a9e0693aaf69..d9236bdab42a 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -16,6 +16,7 @@
#include <linux/seq_file.h>
#include <linux/suspend.h>
#include <linux/syscalls.h>
+#include <linux/timekeeping.h>
#include <linux/pm_runtime.h>
#include "power.h"
@@ -321,6 +322,7 @@ struct suspend_stats {
u64 last_hw_sleep;
u64 total_hw_sleep;
u64 max_hw_sleep;
+ struct timespec64 last_success_resume_time;
enum suspend_stat_step failed_steps[REC_FAILED_NUM];
};
@@ -361,6 +363,17 @@ void dpm_save_errno(int err)
suspend_stats.last_failed_errno %= REC_FAILED_NUM;
}
+void dpm_save_success_time(int err)
+{
+ /*
+ * Record last succeeded resume timestamp just before thawing processes.
+ * This is for helping users to measure user-space resume performance
+ * for improving their programs or finding regressions.
+ */
+ if (!err)
+ ktime_get_ts64(&suspend_stats.last_success_resume_time);
+}
+
void pm_report_hw_sleep_time(u64 t)
{
suspend_stats.last_hw_sleep = t;
@@ -460,6 +473,17 @@ static ssize_t last_failed_step_show(struct kobject *kobj,
}
static struct kobj_attribute last_failed_step = __ATTR_RO(last_failed_step);
+static ssize_t last_success_resume_time_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%llu.%llu\n",
+ (unsigned long long)suspend_stats.last_success_resume_time.tv_sec,
+ (unsigned long long)suspend_stats.last_success_resume_time.tv_nsec);
+}
+
+static struct kobj_attribute last_success_resume_time =
+ __ATTR_RO(last_success_resume_time);
+
static struct attribute *suspend_attrs[] = {
&success.attr,
&fail.attr,
@@ -477,6 +501,7 @@ static struct attribute *suspend_attrs[] = {
&last_hw_sleep.attr,
&total_hw_sleep.attr,
&max_hw_sleep.attr,
+ &last_success_resume_time.attr,
NULL,
};
@@ -542,6 +567,9 @@ static int suspend_stats_show(struct seq_file *s, void *unused)
seq_printf(s, "\t\t\t%-s\n",
suspend_step_names[suspend_stats.failed_steps[index]]);
}
+ seq_printf(s, "last_success_resume_time:\t%-llu.%llu\n",
+ (unsigned long long)suspend_stats.last_success_resume_time.tv_sec,
+ (unsigned long long)suspend_stats.last_success_resume_time.tv_nsec);
return 0;
}
diff --git a/kernel/power/power.h b/kernel/power/power.h
index de0e6b1077f2..70726a55a9d1 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -348,3 +348,4 @@ static inline void pm_sleep_enable_secondary_cpus(void)
}
void dpm_save_errno(int err);
+void dpm_save_success_time(int err);
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 09f8397bae15..1e561eb6681a 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -601,6 +601,7 @@ static int enter_state(suspend_state_t state)
Finish:
events_check_enabled = false;
pm_pr_dbg("Finishing wakeup.\n");
+ dpm_save_success_time(error);
suspend_finish();
Unlock:
mutex_unlock(&system_transition_mutex);
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