| .. _drm-client-usage-stats: |
| |
| ====================== |
| DRM client usage stats |
| ====================== |
| |
| DRM drivers can choose to export partly standardised text output via the |
| `fops->show_fdinfo()` as part of the driver specific file operations registered |
| in the `struct drm_driver` object registered with the DRM core. |
| |
| One purpose of this output is to enable writing as generic as practicaly |
| feasible `top(1)` like userspace monitoring tools. |
| |
| Given the differences between various DRM drivers the specification of the |
| output is split between common and driver specific parts. Having said that, |
| wherever possible effort should still be made to standardise as much as |
| possible. |
| |
| File format specification |
| ========================= |
| |
| - File shall contain one key value pair per one line of text. |
| - Colon character (`:`) must be used to delimit keys and values. |
| - All keys shall be prefixed with `drm-`. |
| - Whitespace between the delimiter and first non-whitespace character shall be |
| ignored when parsing. |
| - Neither keys or values are allowed to contain whitespace characters. |
| - Numerical key value pairs can end with optional unit string. |
| - Data type of the value is fixed as defined in the specification. |
| |
| Key types |
| --------- |
| |
| 1. Mandatory, fully standardised. |
| 2. Optional, fully standardised. |
| 3. Driver specific. |
| |
| Data types |
| ---------- |
| |
| - <uint> - Unsigned integer without defining the maximum value. |
| - <str> - String excluding any above defined reserved characters or whitespace. |
| |
| Mandatory fully standardised keys |
| --------------------------------- |
| |
| - drm-driver: <str> |
| |
| String shall contain the name this driver registered as via the respective |
| `struct drm_driver` data structure. |
| |
| Optional fully standardised keys |
| -------------------------------- |
| |
| - drm-pdev: <aaaa:bb.cc.d> |
| |
| For PCI devices this should contain the PCI slot address of the device in |
| question. |
| |
| - drm-client-id: <uint> |
| |
| Unique value relating to the open DRM file descriptor used to distinguish |
| duplicated and shared file descriptors. Conceptually the value should map 1:1 |
| to the in kernel representation of `struct drm_file` instances. |
| |
| Uniqueness of the value shall be either globally unique, or unique within the |
| scope of each device, in which case `drm-pdev` shall be present as well. |
| |
| Userspace should make sure to not double account any usage statistics by using |
| the above described criteria in order to associate data to individual clients. |
| |
| - drm-engine-<str>: <uint> ns |
| |
| GPUs usually contain multiple execution engines. Each shall be given a stable |
| and unique name (str), with possible values documented in the driver specific |
| documentation. |
| |
| Value shall be in specified time units which the respective GPU engine spent |
| busy executing workloads belonging to this client. |
| |
| Values are not required to be constantly monotonic if it makes the driver |
| implementation easier, but are required to catch up with the previously reported |
| larger value within a reasonable period. Upon observing a value lower than what |
| was previously read, userspace is expected to stay with that larger previous |
| value until a monotonic update is seen. |
| |
| - drm-engine-capacity-<str>: <uint> |
| |
| Engine identifier string must be the same as the one specified in the |
| drm-engine-<str> tag and shall contain a greater than zero number in case the |
| exported engine corresponds to a group of identical hardware engines. |
| |
| In the absence of this tag parser shall assume capacity of one. Zero capacity |
| is not allowed. |
| |
| - drm-memory-<str>: <uint> [KiB|MiB] |
| |
| Each possible memory type which can be used to store buffer objects by the |
| GPU in question shall be given a stable and unique name to be returned as the |
| string here. |
| |
| Value shall reflect the amount of storage currently consumed by the buffer |
| object belong to this client, in the respective memory region. |
| |
| Default unit shall be bytes with optional unit specifiers of 'KiB' or 'MiB' |
| indicating kibi- or mebi-bytes. |
| |
| - drm-cycles-<str> <uint> |
| |
| Engine identifier string must be the same as the one specified in the |
| drm-engine-<str> tag and shall contain the number of busy cycles for the given |
| engine. |
| |
| Values are not required to be constantly monotonic if it makes the driver |
| implementation easier, but are required to catch up with the previously reported |
| larger value within a reasonable period. Upon observing a value lower than what |
| was previously read, userspace is expected to stay with that larger previous |
| value until a monotonic update is seen. |
| |
| - drm-maxfreq-<str> <uint> [Hz|MHz|KHz] |
| |
| Engine identifier string must be the same as the one specified in the |
| drm-engine-<str> tag and shall contain the maximum frequency for the given |
| engine. Taken together with drm-cycles-<str>, this can be used to calculate |
| percentage utilization of the engine, whereas drm-engine-<str> only reflects |
| time active without considering what frequency the engine is operating as a |
| percentage of it's maximum frequency. |
| |
| =============================== |
| Driver specific implementations |
| =============================== |
| |
| :ref:`i915-usage-stats` |
