[PATCH 1/2] wined3d: Implement wined3d_deferred_context_update_sub_resource().

[Henri Verbeet]

Yes, mostly what Matteo said.

On Fri, 28 May 2021 at 15:39, Matteo Bruni <matteo.mystral at gmail.com> wrote:
> So this is, AFAIR, more or less what the staging patchset did. I don't
> think that we want to put the data in the command stream though.
>
It may not be too bad for deferred contexts, but for immediate
contexts probably not, no.

> Always copying the data from the user-provided source to some other
> storage is definitely the right choice: we don't want to block the
> application (more or less directly) to make sure that the data stays
> around until we need it. That's bad for performance for immediate
> contexts and just impossible for deferred, so not much to argue there.
> At the same time we also want to minimize the amount of copies.
> Ideally, for a GPU resource, here we'd upload the data right to the
> GPU (e.g. inside a persistently mapped buffer), ready to be used
> whenever it's time. For a CPU resource instead we'd copy the data into
> its final place in sysmem (what will eventually become its
> "heap_memory"). We don't quite have the infrastructure for it at the
> moment but that would be the goal IMO.
> What you do in patch 2/2 is more along the lines of this idea. The
> sysmem allocation mechanism works okay for the time being and could be
> extended to handle other types of memory, e.g. it could eventually
> take charge of the vulkan allocator, making it generic and usable from
> GL too. I don't think it has to be managed by each deferred context
> (i.e. it should probably be per-device), although the current scheme
> has the advantage of not having to care about concurrency.
>
> So, at least in my view, I'd bring the allocator bits from patch 2/2
> into patch 1/2 and use that for update_sub_resource, both the deferred
> and the immediate variants (the latter could be its own patch). You'd
> only need the DISCARD portion for update_sub_resource, so the rest can
> (and probably should) stay in the map() patch.
>
My (very rough) proposal for this would be to replace the "data" field
in the wined3d_cs_update_sub_resource structure with a
wined3d_bo_address, and then introduce something like the following:

    static bool wined3d_device_context_get_upload_bo(struct
wined3d_device_context *context,
            struct wined3d_resource *resource, unsigned int
sub_resource_idx, const struct wined3d_box *box,
            uint32_t flags, struct wined3d_bo_address *address, void **map_ptr)
    {
        ...
    }

For deferred contexts you should then be able to do something
(conceptually) very similar to patch 2/2, and in the end we may not
even need map/unmap/update_sub_resource in the
wined3d_device_context_ops structure.