Documentation/gpu/drm-usage-stats.rst - linux - Git at Google

 .. _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 practically
 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.
 - Keys are not 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.
 - <keystr> - String excluding any above defined reserved characters or whitespace.
 - <valstr> - String.

 Mandatory fully standardised keys
 ---------------------------------

 - drm-driver: <valstr>

 String shall contain the name this driver registered as via the respective
 `struct drm_driver` data structure.

 Optional fully standardised keys
 --------------------------------

 Identification
 ^^^^^^^^^^^^^^

 - 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-client-name: <valstr>

 String optionally set by userspace using DRM_IOCTL_SET_CLIENT_NAME.


 Utilization
 ^^^^^^^^^^^

 - drm-engine-<keystr>: <uint> ns

 GPUs usually contain multiple execution engines. Each shall be given a stable
 and unique name (keystr), 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-<keystr>: <uint>

 Engine identifier string must be the same as the one specified in the
 drm-engine-<keystr> 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-cycles-<keystr>: <uint>

 Engine identifier string must be the same as the one specified in the
 drm-engine-<keystr> 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-total-cycles-<keystr>: <uint>

 Engine identifier string must be the same as the one specified in the
 drm-cycles-<keystr> tag and shall contain the total number cycles for the given
 engine.

 This is a timestamp in GPU unspecified unit that matches the update rate
 of drm-cycles-<keystr>. For drivers that implement this interface, the engine
 utilization can be calculated entirely on the GPU clock domain, without
 considering the CPU sleep time between 2 samples.

 A driver may implement either this key or drm-maxfreq-<keystr>, but not both.

 - drm-maxfreq-<keystr>: <uint> [Hz|MHz|KHz]

 Engine identifier string must be the same as the one specified in the
 drm-engine-<keystr> tag and shall contain the maximum frequency for the given
 engine.  Taken together with drm-cycles-<keystr>, this can be used to calculate
 percentage utilization of the engine, whereas drm-engine-<keystr> only reflects
 time active without considering what frequency the engine is operating as a
 percentage of its maximum frequency.

 A driver may implement either this key or drm-total-cycles-<keystr>, but not
 both.

 Memory
 ^^^^^^

 - drm-memory-<region>: <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.

 The region name "memory" is reserved to refer to normal system memory.

 Value shall reflect the amount of storage currently consumed by the buffer
 objects 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.

 This key is deprecated and is an alias for drm-resident-<region>. Only one of
 the two should be present in the output.

 - drm-shared-<region>: <uint> [KiB|MiB]

 The total size of buffers that are shared with another file (e.g., have more
 than a single handle).

 - drm-total-<region>: <uint> [KiB|MiB]

 The total size of all created buffers including shared and private memory. The
 backing store for the buffers does not have to be currently instantiated to be
 counted under this category.

 - drm-resident-<region>: <uint> [KiB|MiB]

 The total size of buffers that are resident (have their backing store present or
 instantiated) in the specified region.

 This is an alias for drm-memory-<region> and only one of the two should be
 present in the output.

 - drm-purgeable-<region>: <uint> [KiB|MiB]

 The total size of buffers that are purgeable.

 For example drivers which implement a form of 'madvise' like functionality can
 here count buffers which have instantiated backing store, but have been marked
 with an equivalent of MADV_DONTNEED.

 - drm-active-<region>: <uint> [KiB|MiB]

 The total size of buffers that are active on one or more engines.

 One practical example of this can be presence of unsignaled fences in an GEM
 buffer reservation object. Therefore the active category is a subset of
 resident.

 Implementation Details
 ======================

 Drivers should use drm_show_fdinfo() in their `struct file_operations`, and
 implement &drm_driver.show_fdinfo if they wish to provide any stats which
 are not provided by drm_show_fdinfo().  But even driver specific stats should
 be documented above and where possible, aligned with other drivers.

 Driver specific implementations
 -------------------------------

 * :ref:`i915-usage-stats`
 * :ref:`panfrost-usage-stats`
 * :ref:`panthor-usage-stats`
 * :ref:`xe-usage-stats`
	.. _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 practically
	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.
	- Keys are not 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.
	- <keystr> - String excluding any above defined reserved characters or whitespace.
	- <valstr> - String.

	Mandatory fully standardised keys
	---------------------------------

	- drm-driver: <valstr>

	String shall contain the name this driver registered as via the respective
	`struct drm_driver` data structure.

	Optional fully standardised keys
	--------------------------------

	Identification
	^^^^^^^^^^^^^^

	- 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-client-name: <valstr>

	String optionally set by userspace using DRM_IOCTL_SET_CLIENT_NAME.


	Utilization
	^^^^^^^^^^^

	- drm-engine-<keystr>: <uint> ns

	GPUs usually contain multiple execution engines. Each shall be given a stable
	and unique name (keystr), 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-<keystr>: <uint>

	Engine identifier string must be the same as the one specified in the
	drm-engine-<keystr> 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-cycles-<keystr>: <uint>

	Engine identifier string must be the same as the one specified in the
	drm-engine-<keystr> 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-total-cycles-<keystr>: <uint>

	Engine identifier string must be the same as the one specified in the
	drm-cycles-<keystr> tag and shall contain the total number cycles for the given
	engine.

	This is a timestamp in GPU unspecified unit that matches the update rate
	of drm-cycles-<keystr>. For drivers that implement this interface, the engine
	utilization can be calculated entirely on the GPU clock domain, without
	considering the CPU sleep time between 2 samples.

	A driver may implement either this key or drm-maxfreq-<keystr>, but not both.

	- drm-maxfreq-<keystr>: <uint> [Hz\|MHz\|KHz]

	Engine identifier string must be the same as the one specified in the
	drm-engine-<keystr> tag and shall contain the maximum frequency for the given
	engine. Taken together with drm-cycles-<keystr>, this can be used to calculate
	percentage utilization of the engine, whereas drm-engine-<keystr> only reflects
	time active without considering what frequency the engine is operating as a
	percentage of its maximum frequency.

	A driver may implement either this key or drm-total-cycles-<keystr>, but not
	both.

	Memory
	^^^^^^

	- drm-memory-<region>: <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.

	The region name "memory" is reserved to refer to normal system memory.

	Value shall reflect the amount of storage currently consumed by the buffer
	objects 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.

	This key is deprecated and is an alias for drm-resident-<region>. Only one of
	the two should be present in the output.

	- drm-shared-<region>: <uint> [KiB\|MiB]

	The total size of buffers that are shared with another file (e.g., have more
	than a single handle).

	- drm-total-<region>: <uint> [KiB\|MiB]

	The total size of all created buffers including shared and private memory. The
	backing store for the buffers does not have to be currently instantiated to be
	counted under this category.

	- drm-resident-<region>: <uint> [KiB\|MiB]

	The total size of buffers that are resident (have their backing store present or
	instantiated) in the specified region.

	This is an alias for drm-memory-<region> and only one of the two should be
	present in the output.

	- drm-purgeable-<region>: <uint> [KiB\|MiB]

	The total size of buffers that are purgeable.

	For example drivers which implement a form of 'madvise' like functionality can
	here count buffers which have instantiated backing store, but have been marked
	with an equivalent of MADV_DONTNEED.

	- drm-active-<region>: <uint> [KiB\|MiB]

	The total size of buffers that are active on one or more engines.

	One practical example of this can be presence of unsignaled fences in an GEM
	buffer reservation object. Therefore the active category is a subset of
	resident.

	Implementation Details
	======================

	Drivers should use drm_show_fdinfo() in their `struct file_operations`, and
	implement &drm_driver.show_fdinfo if they wish to provide any stats which
	are not provided by drm_show_fdinfo(). But even driver specific stats should
	be documented above and where possible, aligned with other drivers.

	Driver specific implementations
	-------------------------------

	* :ref:`i915-usage-stats`
	* :ref:`panfrost-usage-stats`
	* :ref:`panthor-usage-stats`
	* :ref:`xe-usage-stats`