[PATCH 1/2] Documentation/gpu: Document the situation with unqualified drm-memory-

[Rob Clark]

On Tue, Aug 13, 2024 at 6:57 AM Tvrtko Ursulin <tursulin at igalia.com> wrote:
>
> From: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>
>
> Currently it is not well defined what is drm-memory- compared to other
> categories.
>
> In practice the only driver which emits these keys is amdgpu and in them
> exposes the current resident buffer object memory (including shared).
>
> To prevent any confusion, document that drm-memory- is deprecated and an
> alias for drm-resident-memory-.
>
> While at it also clarify that the reserved sub-string 'memory' refers to
> the memory region component, and also clarify the intended semantics of
> other memory categories.
>
> v2:
>  * Also mark drm-memory- as deprecated.
>  * Add some more text describing memory categories. (Alex)
>
> v3:
>  * Semantics of the amdgpu drm-memory is actually as drm-resident.
>
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>
> Cc: Alex Deucher <alexander.deucher at amd.com>
> Cc: Christian König <christian.keonig at amd.com>
> Cc: Rob Clark <robdclark at chromium.org>

Reviewed-by: Rob Clark <robdclark at gmail.com>

> ---
>  Documentation/gpu/drm-usage-stats.rst | 25 ++++++++++++++++++++++---
>  1 file changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/gpu/drm-usage-stats.rst b/Documentation/gpu/drm-usage-stats.rst
> index a80f95ca1b2f..ff964c707754 100644
> --- a/Documentation/gpu/drm-usage-stats.rst
> +++ b/Documentation/gpu/drm-usage-stats.rst
> @@ -144,7 +144,9 @@ Memory
>
>  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 name "memory" is reserved to refer to normal system memory.
> +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.
> @@ -152,6 +154,9 @@ 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
> @@ -159,20 +164,34 @@ than a single handle).
>
>  - drm-total-<region>: <uint> [KiB|MiB]
>
> -The total size of buffers that including shared and private memory.
> +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 in the specified region.
> +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
>  ======================
>
> --
> 2.44.0
>