On 18/11/2024 14:56, Li, Yunxiang (Teddy) wrote:
[Public]
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx>
Sent: Monday, November 18, 2024 9:38
On 16/11/2024 04:44, Yunxiang Li wrote:
Define how to handle buffers with multiple possible placement so we
don't get incompatible implementations. Callout the resident
requirement for drm-purgeable- explicitly. Remove the requirement for
there to be only drm-memory- or only drm-resident-, it's not what's
implemented and having both is better for back-compat. Also re-order
the paragraphs to flow better.
Signed-off-by: Yunxiang Li <Yunxiang.Li@xxxxxxx>
CC: dri-devel@xxxxxxxxxxxxxxxxxxxxx
---
Documentation/gpu/drm-usage-stats.rst | 36 ++++++++++++---------------
1 file changed, 16 insertions(+), 20 deletions(-)
diff --git a/Documentation/gpu/drm-usage-stats.rst
b/Documentation/gpu/drm-usage-stats.rst
index ff964c707754a..973663f91a292 100644
--- a/Documentation/gpu/drm-usage-stats.rst
+++ b/Documentation/gpu/drm-usage-stats.rst
@@ -140,13 +140,9 @@ 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.
+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 used as
the "<region>"
+string. 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.
@@ -154,31 +150,27 @@ 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.
IMO the second sentence should stay in principle (I mean at the new location,
where you moved it). Intent is to avoid new implementations adding both keys. The
fact amdgpu has both is not relevant for that purpose. We don't want someone just
reading it is an alias and having to have any doubt whether they need to output both
or not.
I see, yeah I will mention in the drm-memory- part that that tag is legacy amdgpu only behavior.
+- 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 count under this category. To avoid double
+counting, if a buffer falls under multiple regions, the
+implementation should pick only one of the regions, and do so in a consistent
manner.
Addition feels fine to me in principle. I would only suggest rewording it a bit to avoid
ambiguity about what it means to "fall under". Perhaps like this:
To avoid double counting when buffers can be instantiated in one of the multiple
allowed memory regions, the implementation should account the total against only
one of the regions, and should pick this region in a consistent manner.
Ack
- 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.
+than a single handle). Same caveat as drm-total- applies.
I suggest to explicitly point out the caveat is the multiple region one.
and Ack
- 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.
I think it does not harm to keep this note at both keys. Or at least make one
reference the other for this point specifically.
Might be easier to just have drm-memory- as a foot note here, instead of its own section
Not entirely sure but as long as the legacy and one key note is easily
spotted when reading either of the two it works for me.
-
- drm-purgeable-<region>: <uint> [KiB|MiB]
-The total size of buffers that are purgeable.
+The total size of buffers that are resident and purgeable.
Is it not redundant? How could something not resident be purgeable in the first
place?
There is the possible confusion between buffers having a purgeable bit and buffers in a state that is purgeable, I feel like it's worth an explicit callout since there's also code comments about this difference.
Hm I don't follow this. If you are talking about some implementation
details does someone viewing this from the outside cares? Anyway, the
addition does not harm, just that I don't see the need. Feel free to
leave it.
Regards,
Tvrtko
For example drivers which implement a form of 'madvise' like functionality can
here count buffers which have instantiated backing store, but have
been marked @@ -192,6 +184,10 @@ 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.
+- drm-memory-<region>: <uint> [KiB|MiB]
+
+This key is deprecated and is an alias for drm-resident-<region> if present.
+
Implementation Details
======================
Regards,
Tvrtko
