Power-of-two SW stack sizes are prone to causing collisions in the
hashing function used by the L3 to map memory addresses to banks,
which can cause stack accesses from most DSSes to bottleneck on a
single L3 bank. Fix it by padding the SW stack stride by a single
cacheline if it was a power of two. This has been reported by Felix
DeGrood to improve Quake2 RTX performance by ~30% on DG2-512 in
combination with other RT patches Lionel Landwerlin has been working
on.
Many thanks to Felix DeGrood for doing much of the legwork and
providing several iterations of Q2RTX performance counter dumps which
eventually prompted me to consider the hash collision theory and
motivated this patch, and for providing additional performance counter
dumps confirming that there is no longer an appreciable imbalance in
traffic across L3 banks after this change.
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21461>
They're not really "push" anymore but that's because there is no such
thing as push constants in bindless shaders on Intel. They should be
fast enough, though. There is some room for debate here as to whether
we want to do the pull in NIR or push it into the back-end. The
advantage of doing it in the back-end is that it'd be easier to use
MOV_INDIRECT for indirect push constant access rather than falling back
to a dataport message.
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7356>
Unlike graphics and compute pipelines, Vulkan ray-tracing pipelines do
not have a single entrypoint. Instead, the raygen shader is specified
as a one-element shader binding table in the vkCmdTraceRay call. This
means that raygen shaders have to be bindless shaders just like any
other ray tracing shader. To launch them, we have a tiny compute shader
that acts as a trampoline and sets up the hotzone and uses btd_spawn to
fire off the raygen shader.
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7356>
