| Message ID | 6b705dc178d484dd4f99e6bd134bdf09ee0a879e.1718787627.git.perry.yuan@amd.com (mailing list archive) |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | Mario Limonciello |
| Headers | show |
| Series | AMD Pstate Driver Core Performance Boost | expand |
On 6/19/2024 04:16, Perry Yuan wrote: > Updates the documentation in `amd-pstate.rst` to include information about the > per CPU boost control feature. Users can now enable or disable the Core Performance > Boost (CPB) feature on individual CPUs using the `boost` sysfs attribute. > > Signed-off-by: Perry Yuan <perry.yuan@amd.com> > Reviewed-by: Mario Limonciello <mario.limonciello@amd.com> > --- > Documentation/admin-guide/pm/amd-pstate.rst | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst > index bcc0d9404c18..98e43c53c387 100644 > --- a/Documentation/admin-guide/pm/amd-pstate.rst > +++ b/Documentation/admin-guide/pm/amd-pstate.rst > @@ -281,6 +281,26 @@ integer values defined between 0 to 255 when EPP feature is enabled by platform > firmware, if EPP feature is disabled, driver will ignore the written value > This attribute is read-write. > > +``boost`` > +The `boost` sysfs attribute provides control over the CPU core > +performance boost, allowing users to manage the maximum frequency limitation > +of the CPU. This attribute can be used to enable or disable the boost feature > +on individual CPUs. > + > +When the boost feature is enabled, the CPU can dynamically increase its frequency > +beyond the base frequency, providing enhanced performance for demanding workloads. > +On the other hand, disabling the boost feature restricts the CPU to operate at the > +base frequency, which may be desirable in certain scenarios to prioritize power > +efficiency or manage temperature. > + > +To manipulate the `boost` attribute, users can write a value of `0` to disable the > +boost or `1` to enable it, for the respective CPU using the sysfs path > +`/sys/devices/system/cpu/cpuX/cpufreq/boost`, where `X` represents the CPU number. > + > +It is important to note that modifying the global variable > +`amd_pstate_global_params.cpb_boost` will override the individual CPU settings. The whole point of the global cpb_boost is an easy way for software to turn on/off for the whole package. This makes me wonder if we want a "custom" string for the global param if one of the CPUs has been individually modified separately from the global flag. Then software can very easily tell when it's been toggled for a given CPU or via the global flag. * Basically if userspace wrote to a single CPU store a bit in the global structure to say cpb_custom = true if it's not already set. * If writing to cpb_boost from sysfs then "cpb_custom = false" * If reading cpb_boost from sysfs and "cpb_custom = true" then double check all CPUs. - If they don't have the same value return "custom". - If they all have the same values this means software has updated them all, set "cpb_custom = false" and then return enabled/disabled. What do you think? > + > + > Other performance and frequency values can be read back from > ``/sys/devices/system/cpu/cpuX/acpi_cppc/``, see :ref:`cppc_sysfs`. >
Mario Limonciello <mario.limonciello@amd.com> writes: > On 6/19/2024 04:16, Perry Yuan wrote: >> Updates the documentation in `amd-pstate.rst` to include information about the >> per CPU boost control feature. Users can now enable or disable the Core Performance >> Boost (CPB) feature on individual CPUs using the `boost` sysfs attribute. >> >> Signed-off-by: Perry Yuan <perry.yuan@amd.com> >> Reviewed-by: Mario Limonciello <mario.limonciello@amd.com> >> --- >> Documentation/admin-guide/pm/amd-pstate.rst | 20 ++++++++++++++++++++ >> 1 file changed, 20 insertions(+) >> >> diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst >> index bcc0d9404c18..98e43c53c387 100644 >> --- a/Documentation/admin-guide/pm/amd-pstate.rst >> +++ b/Documentation/admin-guide/pm/amd-pstate.rst >> @@ -281,6 +281,26 @@ integer values defined between 0 to 255 when EPP feature is enabled by platform >> firmware, if EPP feature is disabled, driver will ignore the written value >> This attribute is read-write. >> >> +``boost`` >> +The `boost` sysfs attribute provides control over the CPU core >> +performance boost, allowing users to manage the maximum frequency limitation >> +of the CPU. This attribute can be used to enable or disable the boost feature >> +on individual CPUs. >> + >> +When the boost feature is enabled, the CPU can dynamically increase its frequency >> +beyond the base frequency, providing enhanced performance for demanding workloads. >> +On the other hand, disabling the boost feature restricts the CPU to operate at the >> +base frequency, which may be desirable in certain scenarios to prioritize power >> +efficiency or manage temperature. >> + >> +To manipulate the `boost` attribute, users can write a value of `0` to disable the >> +boost or `1` to enable it, for the respective CPU using the sysfs path >> +`/sys/devices/system/cpu/cpuX/cpufreq/boost`, where `X` represents the CPU number. >> + >> +It is important to note that modifying the global variable >> +`amd_pstate_global_params.cpb_boost` will override the individual CPU settings. > > The whole point of the global cpb_boost is an easy way for software to > turn on/off for the whole package. > > This makes me wonder if we want a "custom" string for the global param > if one of the CPUs has been individually modified separately from the > global flag. Then software can very easily tell when it's been toggled > for a given CPU or via the global flag. Yeah, this is one usecase which may justify the need for a separate amd_pstate/cpb_boost interface. i.e., if there are users who do want to reset the boost state on all the CPUs if individual CPUs have independently toggled the boost states. > > * Basically if userspace wrote to a single CPU store a bit in the global > structure to say cpb_custom = true if it's not already set. > * If writing to cpb_boost from sysfs then "cpb_custom = false" > * If reading cpb_boost from sysfs and "cpb_custom = true" then double > check all CPUs. Actually, we can maintain a counter which is set to nr_online_cpus when the global cpb_boost is enabled and set to 0 when global cpb_boost is disabled. When each individual CPU disables cpb , we decrement the value of the counter. We increment the counter value when some individual CPU enables cpb. So global counter returns "enabled" if counter == nr_policies, returns "disabled" if counter == 0 and "custom" for all other values of the counter. > - If they don't have the same value return "custom". > - If they all have the same values this means software has updated > them all, set "cpb_custom = false" and then return enabled/disabled. > > What do you think? Could be done. But again, are there users who want to see the "custom" value ? -- Thanks and Regards gautham.
diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst index bcc0d9404c18..98e43c53c387 100644 --- a/Documentation/admin-guide/pm/amd-pstate.rst +++ b/Documentation/admin-guide/pm/amd-pstate.rst @@ -281,6 +281,26 @@ integer values defined between 0 to 255 when EPP feature is enabled by platform firmware, if EPP feature is disabled, driver will ignore the written value This attribute is read-write. +``boost`` +The `boost` sysfs attribute provides control over the CPU core +performance boost, allowing users to manage the maximum frequency limitation +of the CPU. This attribute can be used to enable or disable the boost feature +on individual CPUs. + +When the boost feature is enabled, the CPU can dynamically increase its frequency +beyond the base frequency, providing enhanced performance for demanding workloads. +On the other hand, disabling the boost feature restricts the CPU to operate at the +base frequency, which may be desirable in certain scenarios to prioritize power +efficiency or manage temperature. + +To manipulate the `boost` attribute, users can write a value of `0` to disable the +boost or `1` to enable it, for the respective CPU using the sysfs path +`/sys/devices/system/cpu/cpuX/cpufreq/boost`, where `X` represents the CPU number. + +It is important to note that modifying the global variable +`amd_pstate_global_params.cpb_boost` will override the individual CPU settings. + + Other performance and frequency values can be read back from ``/sys/devices/system/cpu/cpuX/acpi_cppc/``, see :ref:`cppc_sysfs`.