Power Management

The goal of power management is to manage and save power consumed by the device in the following states:

idle => whenever no request is sent, power state is minimum.
initialized or reset.
active => whenever there are requests to be handled, power state is max.

Configuration

Out-of-Tree

When using the Out-of-Tree QAT package, Power management configuration is included in the device configuration file (i.e. /etc/4xxx_devX.conf where X is the 0-based index of the device.)

Power management configurations parameters include:

Power Management Configuration
Parameter	Description
`PmIdleSupport`	Configure the device to enable/disable power management idle supporting. Power management idle support is enabled by default.

In-Tree

When using the in-tree solution, Power Management configuration is handled via sysfs-driver-qat.

For details refer to sysfs-driver-qat documentation.

Usage

The information of power management status are exposed in debug sysfs file /sys/kernel/debug/qat_4xxx_AAAA:BB:CC.D/pm_status where:

AAAA:BB:CC.D is the Domain:BDF of the target Intel® QAT Endpoint.

Example:

cat /sys/kernel/debug/qat_4xxx_0000:6b:00.0/pm_status

The QAT device is statically configured, so any change in device configuration file will only be effective after the device is rebooted.

Considerations

While power management is an important feature in reducing power consumed, it can affect the internal components’ clocks of QAT devices, and that can affect example telemetry work. It also can impact latency numbers.

Important

It is recommended to disable the power management feature if either of the following is true:

Using feature dependent on clock speed, such as telemetry, or
Supporting latency-sensitive workload.