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

[Alex Deucher]

On Wed, Sep 4, 2024 at 4:36 AM Tvrtko Ursulin <tvrtko.ursulin at igalia.com> wrote:
>
>
> On 21/08/2024 21:47, Alex Deucher wrote:
> > On Tue, Aug 13, 2024 at 9:57 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>
> >> ---
> >>   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.
> >> +
> >
> > I'm not sure how best to handle this.  What should amdgpu do?  We have
> > customers out in the field using these existing fields and then with
> > patch 2, they go away.  Arguably we'd want both for backwards
> > compatibility.
>
> Exactly, so it looks you maybe missed that 2/2 is not removing the
> amdgpu "legacy" drm-memory-. It keeps outputting it and also duplicating
> under drm-resident-. This is mentioned in the commit paragraph:
>
> """
> Legacy keys have been preserved, with the outlook of only potentially
> removing only the drm-memory- when the time gets right.
> """
>
> Put differently, I don't think 2/2 should break the existing
> tools/parsers. Only if they have hardcoded assumptions about the order
> of keys perhaps?

You're right.  I totally missed that part.  The series is:
Reviewed-by: Alex Deucher <alexander.deucher at amd.com>
Happy to take the patches through my tree or patch 2 via mine and
patch 1 via drm-misc.

Alex

>
> Regards,
>
> Tvrtko
>
> >>   - 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
> >>