1.. _drm-client-usage-stats: 2 3====================== 4DRM client usage stats 5====================== 6 7DRM drivers can choose to export partly standardised text output via the 8`fops->show_fdinfo()` as part of the driver specific file operations registered 9in the `struct drm_driver` object registered with the DRM core. 10 11One purpose of this output is to enable writing as generic as practically 12feasible `top(1)` like userspace monitoring tools. 13 14Given the differences between various DRM drivers the specification of the 15output is split between common and driver specific parts. Having said that, 16wherever possible effort should still be made to standardise as much as 17possible. 18 19File format specification 20========================= 21 22- File shall contain one key value pair per one line of text. 23- Colon character (`:`) must be used to delimit keys and values. 24- All keys shall be prefixed with `drm-`. 25- Whitespace between the delimiter and first non-whitespace character shall be 26 ignored when parsing. 27- Keys are not allowed to contain whitespace characters. 28- Numerical key value pairs can end with optional unit string. 29- Data type of the value is fixed as defined in the specification. 30 31Key types 32--------- 33 341. Mandatory, fully standardised. 352. Optional, fully standardised. 363. Driver specific. 37 38Data types 39---------- 40 41- <uint> - Unsigned integer without defining the maximum value. 42- <keystr> - String excluding any above defined reserved characters or whitespace. 43- <valstr> - String. 44 45Mandatory fully standardised keys 46--------------------------------- 47 48- drm-driver: <valstr> 49 50String shall contain the name this driver registered as via the respective 51`struct drm_driver` data structure. 52 53Optional fully standardised keys 54-------------------------------- 55 56Identification 57^^^^^^^^^^^^^^ 58 59- drm-pdev: <aaaa:bb.cc.d> 60 61For PCI devices this should contain the PCI slot address of the device in 62question. 63 64- drm-client-id: <uint> 65 66Unique value relating to the open DRM file descriptor used to distinguish 67duplicated and shared file descriptors. Conceptually the value should map 1:1 68to the in kernel representation of `struct drm_file` instances. 69 70Uniqueness of the value shall be either globally unique, or unique within the 71scope of each device, in which case `drm-pdev` shall be present as well. 72 73Userspace should make sure to not double account any usage statistics by using 74the above described criteria in order to associate data to individual clients. 75 76Utilization 77^^^^^^^^^^^ 78 79- drm-engine-<keystr>: <uint> ns 80 81GPUs usually contain multiple execution engines. Each shall be given a stable 82and unique name (keystr), with possible values documented in the driver specific 83documentation. 84 85Value shall be in specified time units which the respective GPU engine spent 86busy executing workloads belonging to this client. 87 88Values are not required to be constantly monotonic if it makes the driver 89implementation easier, but are required to catch up with the previously reported 90larger value within a reasonable period. Upon observing a value lower than what 91was previously read, userspace is expected to stay with that larger previous 92value until a monotonic update is seen. 93 94- drm-engine-capacity-<keystr>: <uint> 95 96Engine identifier string must be the same as the one specified in the 97drm-engine-<keystr> tag and shall contain a greater than zero number in case the 98exported engine corresponds to a group of identical hardware engines. 99 100In the absence of this tag parser shall assume capacity of one. Zero capacity 101is not allowed. 102 103- drm-cycles-<keystr>: <uint> 104 105Engine identifier string must be the same as the one specified in the 106drm-engine-<keystr> tag and shall contain the number of busy cycles for the given 107engine. 108 109Values are not required to be constantly monotonic if it makes the driver 110implementation easier, but are required to catch up with the previously reported 111larger value within a reasonable period. Upon observing a value lower than what 112was previously read, userspace is expected to stay with that larger previous 113value until a monotonic update is seen. 114 115- drm-maxfreq-<keystr>: <uint> [Hz|MHz|KHz] 116 117Engine identifier string must be the same as the one specified in the 118drm-engine-<keystr> tag and shall contain the maximum frequency for the given 119engine. Taken together with drm-cycles-<keystr>, this can be used to calculate 120percentage utilization of the engine, whereas drm-engine-<keystr> only reflects 121time active without considering what frequency the engine is operating as a 122percentage of its maximum frequency. 123 124Memory 125^^^^^^ 126 127- drm-memory-<region>: <uint> [KiB|MiB] 128 129Each possible memory type which can be used to store buffer objects by the 130GPU in question shall be given a stable and unique name to be returned as the 131string here. The name "memory" is reserved to refer to normal system memory. 132 133Value shall reflect the amount of storage currently consumed by the buffer 134objects belong to this client, in the respective memory region. 135 136Default unit shall be bytes with optional unit specifiers of 'KiB' or 'MiB' 137indicating kibi- or mebi-bytes. 138 139- drm-shared-<region>: <uint> [KiB|MiB] 140 141The total size of buffers that are shared with another file (e.g., have more 142than a single handle). 143 144- drm-total-<region>: <uint> [KiB|MiB] 145 146The total size of buffers that including shared and private memory. 147 148- drm-resident-<region>: <uint> [KiB|MiB] 149 150The total size of buffers that are resident in the specified region. 151 152- drm-purgeable-<region>: <uint> [KiB|MiB] 153 154The total size of buffers that are purgeable. 155 156- drm-active-<region>: <uint> [KiB|MiB] 157 158The total size of buffers that are active on one or more engines. 159 160Implementation Details 161====================== 162 163Drivers should use drm_show_fdinfo() in their `struct file_operations`, and 164implement &drm_driver.show_fdinfo if they wish to provide any stats which 165are not provided by drm_show_fdinfo(). But even driver specific stats should 166be documented above and where possible, aligned with other drivers. 167 168Driver specific implementations 169------------------------------- 170 171:ref:`i915-usage-stats` 172:ref:`panfrost-usage-stats` 173