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Message-ID: <MN0PR12MB6101BDD7A3DB5AD251B63495E29A9@MN0PR12MB6101.namprd12.prod.outlook.com>
Date: Tue, 11 Apr 2023 21:49:30 +0000
From: "Limonciello, Mario" <Mario.Limonciello@....com>
To: Hans de Goede <hdegoede@...hat.com>,
Box David E <david.e.box@...el.com>,
"jstultz@...gle.com" <jstultz@...gle.com>,
"pavel@....cz" <pavel@....cz>,
"svenva@...omium.org" <svenva@...omium.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Len Brown <len.brown@...el.com>
CC: "S-k, Shyam-sundar" <Shyam-sundar.S-k@....com>,
"rrangel@...omium.org" <rrangel@...omium.org>,
Jain Rajat <rajatja@...gle.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: RE: [PATCH v7 1/4] PM: Add sysfs files to represent time spent in
hardware sleep state
[Public]
>
> On 4/11/23 23:17, 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>
> > ---
> > v6->v7:
> > * Rename to max_hw_sleep (David E Box)
> > * Drop overflow checks (David E Box)
> > 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 | 24 ++++++++++++++++
> > include/linux/suspend.h | 5 ++++
> > kernel/power/main.c | 40 +++++++++++++++++++++++++++
> > 3 files changed, 69 insertions(+)
> >
> > diff --git a/Documentation/ABI/testing/sysfs-power
> b/Documentation/ABI/testing/sysfs-power
> > index f99d433ff311..0723b4dadfbe 100644
> > --- a/Documentation/ABI/testing/sysfs-power
> > +++ b/Documentation/ABI/testing/sysfs-power
> > @@ -413,6 +413,30 @@ 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.
>
> Hmm I thought that the plan was to add a separate sysfs attr with
> the max time that the hw could represent here, so that userspace
> actually know what constitutes a "longer sleep cycle" ?
>
> That would seem better then such a handwavy comment in the ABI docs?
I obviously misunderstood what you were suggesting.
I don't believe we have a way to programmatically determine what the hardware
Internally uses for it's counter to know this.
So it would need to be a table of some sorts that a given system can support
such value. If we do that, we can actually know whether to return an error code
like -EOVERFLOW or -EINVAL too if the suspend was too long.
I would need Intel guys to share this information though which systems have
which size of counters to make this happen.
>
> > +
> > +What: /sys/power/suspend_stats/max_hw_sleep
> > +Date: June 2023
> > +Contact: Mario Limonciello <mario.limonciello@....com>
> > +Description:
> > + The /sys/power/suspend_stats/max_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.
>
> Maybe "total_hw_sleep" instead of "max_hw_sleep" ? Also since max to
> me sounds like the limit of the longest sleep the hw counters can
> register, so that is bit confusing with the discussion about those
> limits.
total_hw_sleep is actually what was in v6 and max_hw_sleep is what suggested.
That's why I got confused about what you guys meant.
>
> Regards,
>
> Hans
>
>
>
> > +
> > 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..819e9677fd10 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 max_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..a5546b91ecc9 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 +84,13 @@ 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;
> > + suspend_stats.max_hw_sleep += t;
> > +}
> > +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 +385,22 @@ 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 max_hw_sleep_show(struct kobject *kobj,
> > + struct kobj_attribute *attr, char *buf)
> > +{
> > + if (suspend_stats.max_hw_sleep == -EOVERFLOW)
> > + return suspend_stats.max_hw_sleep;
> > + return sysfs_emit(buf, "%llu\n", suspend_stats.max_hw_sleep);
> > +}
> > +static struct kobj_attribute max_hw_sleep =
> __ATTR_RO(max_hw_sleep);
> > +
> > static struct attribute *suspend_attrs[] = {
> > &success.attr,
> > &fail.attr,
> > @@ -391,12 +415,28 @@ static struct attribute *suspend_attrs[] = {
> > &last_failed_dev.attr,
> > &last_failed_errno.attr,
> > &last_failed_step.attr,
> > + &last_hw_sleep.attr,
> > + &max_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 != &max_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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