Since 4a94bfc2f6 we segregate
different D3D12 descriptor types in different Vulkan descriptor sets.
This change was introduced to reduce descriptor wasting when
allocating a new descriptor pool; that can be very useful when
using virtual heaps, which have to often cycle through many
descriptors, but it is expected to have limited impact for Vulkan
heaps, given that in that case most descriptors are allocated through
the descriptor heap rather than through the command allocator.
Instead, it has a rather detrimental effect with Vulkan heaps,
because it tends to use many more Vulkan descriptor sets than
necessary, often with just a handful of descriptors each. This
causes a regression on some Vulkan implementations that support
too few descriptor sets.
With this change we revert to a situation similar to before,
stuffing all the descriptors that do not live in a root
descriptor table in as few descriptor sets as possible (at most
one or two, depending on whether push descriptors are used).
We're already implicitly using it for image layouts in which
either depth or stencil is writeable and the other is not.
Correspondingly, add the _KHR suffix in those cases, so the
extension usage is more evident.
According to the Vulkan Hardware Database, only four reports
without this extension were filed since 2023, and all of them
for configurations we likely don't target.
When the client acquires the Vulkan queue it has to ensure that
it is not submitting work before other work it depends on already
submitted through the Direct3D 12 API but currently in the internal
vkd3d queue. Currently we suggest to enqueue signalling a fence and
than wait for it before acquiring the Vulkan queue, which is
correct but excessive: it will wait not just for the work currently
in the queue to be submitted, but for it to be executed too,
introducing useless dependencies.
By adding a way to enqueue signalling a fence on the CPU side we
allow the client to wait for the currently outstanding work to
be submitted to Vulkan, but nothing more.
We're explicitly replacing zero with one in the only place where the
plane count being zero or one makes a difference. It also make sense:
UNKNOWN is used for buffers, which for all intents and purposes have one
plane.
Otherwise ubsan reports runtime errors such as:
libs/vkd3d-shader/ir.c:4731:5: runtime error: null pointer passed as argument 1, which is declared to never be null
Currently, when using Vulkan heaps, we create descriptor set
layouts with as many descriptors as allowed by the Vulkan
implementation limits. For some implementations this can mean
hundreds of millions of descriptors or more, which is wasteful,
given that even on the best resource binding tier Direct3D 12
applications should not expect to have more than a million usable
descriptors.
Recently this began being a problem, because since Mesa 24.2.7
the Intel driver advertises more than 200 million descriptors,
but pipeline compilation takes linear RAM in the number of
descriptors declared in the pipeline layout. This means that
compiling even a simple shader requires 10-20 GB of RAM.
In order to avoid using too much memory, with this commit we clamp
the number of descriptors declared in the set layouts to how many
we actually need to guarantee tier 3 resource binding support.
Creating a pool of 16k descriptors is wasteful if an allocator only uses
a fraction of them, so start at 1k and double for each subsequent
allocation until 16k is reached.
Now that our Vulkan descriptor sets contain only a single vkd3d
descriptor type, we're able to create descriptor pools containing only a
single vkd3d descriptor type as well. This avoids wasting unallocated
descriptors of one type when we run out of descriptors of another type.