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Message-ID: <b6000a3d5d4d6a3e9f8a57414c0b795e8cff6855.camel@intel.com>
Date: Wed, 5 Apr 2023 00:42:27 +0000
From: "Box, David E" <david.e.box@...el.com>
To: "Brown, Len" <len.brown@...el.com>,
"jstultz@...gle.com" <jstultz@...gle.com>,
"pavel@....cz" <pavel@....cz>,
"mario.limonciello@....com" <mario.limonciello@....com>,
"svenva@...omium.org" <svenva@...omium.org>,
"rafael@...nel.org" <rafael@...nel.org>
CC: "hdegoede@...hat.com" <hdegoede@...hat.com>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
"Shyam-sundar.S-k@....com" <Shyam-sundar.S-k@....com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"platform-driver-x86@...r.kernel.org"
<platform-driver-x86@...r.kernel.org>,
"rrangel@...omium.org" <rrangel@...omium.org>,
"Jain, Rajat" <rajatja@...gle.com>
Subject: Re: [PATCH v6 1/4] PM: Add sysfs files to represent time spent in
hardware sleep state
Hi Mario,
On Mon, 2023-04-03 at 16:18 -0500, Mario Limonciello wrote:
> Userspace can't easily discover how much of a sleep cycle was spent in a
> hardware sleep state without using kernel tracing and vendor specific sysfs
> or debugfs files.
>
> To make this information more discoverable, introduce two new sysfs files:
> 1) The time spent in a hw sleep state for last cycle.
> 2) The time spent in a hw sleep state since the kernel booted
> Both of these files will be present only if the system supports s2idle.
>
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
> v5->v6:
> * Add total attribute as well
> * Change text for documentation
> * Adjust flow of is_visible callback.
> * If overflow was detected in total attribute return -EOVERFLOW
> * Rename symbol
> * Add stub for symbol for builds without CONFIG_PM_SLEEP
> v4->v5:
> * Provide time in microseconds instead of percent. Userspace can convert
> this if desirable.
> ---
> Documentation/ABI/testing/sysfs-power | 27 ++++++++++++++++
> include/linux/suspend.h | 5 +++
> kernel/power/main.c | 45 +++++++++++++++++++++++++++
> 3 files changed, 77 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-power
> b/Documentation/ABI/testing/sysfs-power
> index f99d433ff311..37240575d282 100644
> --- a/Documentation/ABI/testing/sysfs-power
> +++ b/Documentation/ABI/testing/sysfs-power
> @@ -413,6 +413,33 @@ Description:
> The /sys/power/suspend_stats/last_failed_step file contains
> the last failed step in the suspend/resume path.
>
> +What: /sys/power/suspend_stats/last_hw_sleep
> +Date: June 2023
> +Contact: Mario Limonciello <mario.limonciello@....com>
> +Description:
> + The /sys/power/suspend_stats/last_hw_sleep file
> + contains the duration of time spent in a hardware sleep
> + state in the most recent system suspend-resume cycle.
> + This number is measured in microseconds.
> +
> + NOTE: Limitations in the size of the hardware counters may
> + cause this value to be inaccurate in longer sleep cycles.
> +
> +What: /sys/power/suspend_stats/total_hw_sleep
> +Date: June 2023
> +Contact: Mario Limonciello <mario.limonciello@....com>
> +Description:
> + The /sys/power/suspend_stats/total_hw_sleep file
> + contains the aggregate of time spent in a hardware sleep
> + state since the kernel was booted. This number
> + is measured in microseconds.
> +
> + NOTE: Limitations in the size of the hardware counters may
> + cause this value to be inaccurate in longer sleep cycles.
> +
> + If an overflow has been detected this file will return
> + -EOVERFLOW.
> +
> What: /sys/power/sync_on_suspend
> Date: October 2019
> Contact: Jonas Meurer <jonas@...esources.org>
> diff --git a/include/linux/suspend.h b/include/linux/suspend.h
> index cfe19a028918..069ef0c0ae57 100644
> --- a/include/linux/suspend.h
> +++ b/include/linux/suspend.h
> @@ -68,6 +68,8 @@ struct suspend_stats {
> int last_failed_errno;
> int errno[REC_FAILED_NUM];
> int last_failed_step;
> + u64 last_hw_sleep;
> + u64 total_hw_sleep;
> enum suspend_stat_step failed_steps[REC_FAILED_NUM];
> };
>
> @@ -489,6 +491,7 @@ void restore_processor_state(void);
> extern int register_pm_notifier(struct notifier_block *nb);
> extern int unregister_pm_notifier(struct notifier_block *nb);
> extern void ksys_sync_helper(void);
> +extern void pm_report_hw_sleep_time(u64 t);
>
> #define pm_notifier(fn, pri) { \
> static struct notifier_block fn##_nb = \
> @@ -526,6 +529,8 @@ static inline int unregister_pm_notifier(struct
> notifier_block *nb)
> return 0;
> }
>
> +static inline void pm_report_hw_sleep_time(u64 t) {};
> +
> static inline void ksys_sync_helper(void) {}
>
> #define pm_notifier(fn, pri) do { (void)(fn); } while (0)
> diff --git a/kernel/power/main.c b/kernel/power/main.c
> index 31ec4a9b9d70..ffd4dd43cbdd 100644
> --- a/kernel/power/main.c
> +++ b/kernel/power/main.c
> @@ -6,6 +6,7 @@
> * Copyright (c) 2003 Open Source Development Lab
> */
>
> +#include <linux/acpi.h>
> #include <linux/export.h>
> #include <linux/kobject.h>
> #include <linux/string.h>
> @@ -83,6 +84,18 @@ int unregister_pm_notifier(struct notifier_block *nb)
> }
> EXPORT_SYMBOL_GPL(unregister_pm_notifier);
>
> +void pm_report_hw_sleep_time(u64 t)
> +{
> + suspend_stats.last_hw_sleep = t;
> + if (suspend_stats.total_hw_sleep == -EOVERFLOW)
> + return;
> + if (suspend_stats.total_hw_sleep + t < suspend_stats.total_hw_sleep)
> + suspend_stats.total_hw_sleep = -EOVERFLOW;
> + else
> + suspend_stats.total_hw_sleep += t;
total_hw_sleep is u64. At microsecond granularity it will never realistically
overflow and isn't worth the check IMO. The overflow concern comes from the u32
hardware counter, but I don't think there's a good way to detect it.
You could just report the maximum hardware counter time as max_hw_sleep so users
know the value isn't reliable if suspended for longer than that.
David
> +}
> +EXPORT_SYMBOL_GPL(pm_report_hw_sleep_time);
> +
> int pm_notifier_call_chain_robust(unsigned long val_up, unsigned long
> val_down)
> {
> int ret;
> @@ -377,6 +390,22 @@ 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_hw_sleep_show(struct kobject *kobj,
> + struct kobj_attribute *attr, char *buf)
> +{
> + return sysfs_emit(buf, "%llu\n", suspend_stats.last_hw_sleep);
> +}
> +static struct kobj_attribute last_hw_sleep = __ATTR_RO(last_hw_sleep);
> +
> +static ssize_t total_hw_sleep_show(struct kobject *kobj,
> + struct kobj_attribute *attr, char *buf)
> +{
> + if (suspend_stats.total_hw_sleep == -EOVERFLOW)
> + return suspend_stats.total_hw_sleep;
> + return sysfs_emit(buf, "%llu\n", suspend_stats.total_hw_sleep);
> +}
> +static struct kobj_attribute total_hw_sleep = __ATTR_RO(total_hw_sleep);
> +
> static struct attribute *suspend_attrs[] = {
> &success.attr,
> &fail.attr,
> @@ -391,12 +420,28 @@ static struct attribute *suspend_attrs[] = {
> &last_failed_dev.attr,
> &last_failed_errno.attr,
> &last_failed_step.attr,
> + &last_hw_sleep.attr,
> + &total_hw_sleep.attr,
> NULL,
> };
>
> +static umode_t suspend_attr_is_visible(struct kobject *kobj, struct attribute
> *attr, int idx)
> +{
> + if (attr != &last_hw_sleep.attr &&
> + attr != &total_hw_sleep.attr)
> + return 0444;
> +
> +#ifdef CONFIG_ACPI
> + if (acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0)
> + return 0444;
> +#endif
> + return 0;
> +}
> +
> static const struct attribute_group suspend_attr_group = {
> .name = "suspend_stats",
> .attrs = suspend_attrs,
> + .is_visible = suspend_attr_is_visible,
> };
>
> #ifdef CONFIG_DEBUG_FS
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