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-total-cycles-<keystr>: <uint> 116 117Engine identifier string must be the same as the one specified in the 118drm-cycles-<keystr> tag and shall contain the total number cycles for the given 119engine. 120 121This is a timestamp in GPU unspecified unit that matches the update rate 122of drm-cycles-<keystr>. For drivers that implement this interface, the engine 123utilization can be calculated entirely on the GPU clock domain, without 124considering the CPU sleep time between 2 samples. 125 126A driver may implement either this key or drm-maxfreq-<keystr>, but not both. 127 128- drm-maxfreq-<keystr>: <uint> [Hz|MHz|KHz] 129 130Engine identifier string must be the same as the one specified in the 131drm-engine-<keystr> tag and shall contain the maximum frequency for the given 132engine. Taken together with drm-cycles-<keystr>, this can be used to calculate 133percentage utilization of the engine, whereas drm-engine-<keystr> only reflects 134time active without considering what frequency the engine is operating as a 135percentage of its maximum frequency. 136 137A driver may implement either this key or drm-total-cycles-<keystr>, but not 138both. 139 140Memory 141^^^^^^ 142 143- drm-memory-<region>: <uint> [KiB|MiB] 144 145Each possible memory type which can be used to store buffer objects by the 146GPU in question shall be given a stable and unique name to be returned as the 147string here. 148 149The region name "memory" is reserved to refer to normal system memory. 150 151Value shall reflect the amount of storage currently consumed by the buffer 152objects belong to this client, in the respective memory region. 153 154Default unit shall be bytes with optional unit specifiers of 'KiB' or 'MiB' 155indicating kibi- or mebi-bytes. 156 157This key is deprecated and is an alias for drm-resident-<region>. Only one of 158the two should be present in the output. 159 160- drm-shared-<region>: <uint> [KiB|MiB] 161 162The total size of buffers that are shared with another file (e.g., have more 163than a single handle). 164 165- drm-total-<region>: <uint> [KiB|MiB] 166 167The total size of all created buffers including shared and private memory. The 168backing store for the buffers does not have to be currently instantiated to be 169counted under this category. 170 171- drm-resident-<region>: <uint> [KiB|MiB] 172 173The total size of buffers that are resident (have their backing store present or 174instantiated) in the specified region. 175 176This is an alias for drm-memory-<region> and only one of the two should be 177present in the output. 178 179- drm-purgeable-<region>: <uint> [KiB|MiB] 180 181The total size of buffers that are purgeable. 182 183For example drivers which implement a form of 'madvise' like functionality can 184here count buffers which have instantiated backing store, but have been marked 185with an equivalent of MADV_DONTNEED. 186 187- drm-active-<region>: <uint> [KiB|MiB] 188 189The total size of buffers that are active on one or more engines. 190 191One practical example of this can be presence of unsignaled fences in an GEM 192buffer reservation object. Therefore the active category is a subset of 193resident. 194 195Implementation Details 196====================== 197 198Drivers should use drm_show_fdinfo() in their `struct file_operations`, and 199implement &drm_driver.show_fdinfo if they wish to provide any stats which 200are not provided by drm_show_fdinfo(). But even driver specific stats should 201be documented above and where possible, aligned with other drivers. 202 203Driver specific implementations 204------------------------------- 205 206* :ref:`i915-usage-stats` 207* :ref:`panfrost-usage-stats` 208* :ref:`xe-usage-stats` 209