linux-kernel - Re: [RFC v3 1/4] PM: Add a sysfs file to represent the total sleep duration

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Message-ID: <CANDhNCqPWV_dC_wo-CCqBuO0J=5TcRAh5AX335PLft2+w19_tQ@mail.gmail.com>
Date:   Tue, 15 Nov 2022 12:44:14 -0800
From:   John Stultz <jstultz@...gle.com>
To:     Mario Limonciello <mario.limonciello@....com>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <sboyd@...nel.org>,
        Sven van Ashbrook <svenva@...omium.org>,
        Raul Rangel <rrangel@...omium.org>, linux-pm@...r.kernel.org,
        platform-driver-x86@...r.kernel.org,
        Rajneesh Bhardwaj <irenic.rajneesh@...il.com>,
        S-k Shyam-sundar <Shyam-sundar.S-k@....com>,
        Rajat Jain <rajatja@...gle.com>,
        David E Box <david.e.box@...el.com>,
        Hans de Goede <hdegoede@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC v3 1/4] PM: Add a sysfs file to represent the total sleep duration

On Tue, Nov 15, 2022 at 12:02 PM Mario Limonciello
<mario.limonciello@....com> wrote:
>
> For userspace to be able to analyze how much of a suspend cycle was spent
> in the hardware sleep states userspace software has to use kernel trace
> points paired with the file `low_power_idle_system_residency_us` on
> supported systems.
>
> To make this information more discoverable, introduce a new sysfs file
> to represent the duration spent in a sleep state.
> This file will be present and updated during resume for all suspend
> types.
>
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
> RFC v2->v3
>  * Drop one of the sysfs files
>  * Use sysfs_emit instead
>  * Fix symbol name (s/type/time/)
>  * Drop is_visible
>  * Use timespec64 type for suspend stats
>  * Update documentation
>  * Update sysfs file name
> ---
>  Documentation/ABI/testing/sysfs-power |  8 ++++++++
>  include/linux/suspend.h               |  2 ++
>  kernel/power/main.c                   | 15 +++++++++++++++
>  kernel/power/suspend.c                |  2 ++
>  kernel/time/timekeeping.c             |  2 ++
>  5 files changed, 29 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
> index f99d433ff311..3abe20c47e08 100644
> --- a/Documentation/ABI/testing/sysfs-power
> +++ b/Documentation/ABI/testing/sysfs-power
> @@ -413,6 +413,14 @@ 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_total
> +Date:          December 2022
> +Contact:       Mario Limonciello <mario.limonciello@....com>
> +Description:
> +               The /sys/power/suspend_stats/last_total file contains
> +               the total duration of the sleep cycle.
> +               This is measured in microseconds.
> +

Nit/bikeshed: "last_total" seems less straightforward then it should
be? Maybe "total_suspend_time" instead?

> diff --git a/kernel/power/main.c b/kernel/power/main.c
> index 31ec4a9b9d70..f33012860699 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>
> @@ -54,6 +55,11 @@ void unlock_system_sleep(unsigned int flags)
>  }
>  EXPORT_SYMBOL_GPL(unlock_system_sleep);
>
> +void pm_account_suspend_time(const struct timespec64 t)
> +{
> +       suspend_stats.last_total = timespec64_add(suspend_stats.last_total, t);
> +}
> +
>  void ksys_sync_helper(void)
>  {
>         ktime_t start;
> @@ -377,6 +383,14 @@ 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_total_show(struct kobject *kobj,
> +               struct kobj_attribute *attr, char *buf)
> +{
> +       return sysfs_emit(buf, "%llu\n",
> +                         timespec64_to_ns(&suspend_stats.last_total) / NSEC_PER_USEC);
> +}
> +static struct kobj_attribute last_total = __ATTR_RO(last_total);
> +
>  static struct attribute *suspend_attrs[] = {
>         &success.attr,
>         &fail.attr,
> @@ -391,6 +405,7 @@ static struct attribute *suspend_attrs[] = {
>         &last_failed_dev.attr,
>         &last_failed_errno.attr,
>         &last_failed_step.attr,
> +       &last_total.attr,
>         NULL,
>  };

While not identical, this has some overlap with the logic in
kernel/time/timekeeping_debug.c
I wonder if it would make sense to consolidate some of this accounting?

thanks
-john