vulkan: Support FA with any multiple of 8 head sizes #15537
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
The scalar FA shader already handled multiples of 8. The coopmat1 FA shader assumed 16x16x16 and the shared memory allocations need the HSK dimensions padded to a multiple of 16. NVIDIA's coopmat2 implementation requires multiples of 16 for N and K, and needs the matrix dimensions padded and loads clamped. Store the FA pipelines in a map, indexed by the pipeline state.
github-actions
bot
added
testing
qnixsynapse
pushed a commit
to menloresearch/llama.cpp
that referenced
this pull request
Aug 25, 2025
The scalar FA shader already handled multiples of 8. The coopmat1 FA shader assumed 16x16x16 and the shared memory allocations need the HSK dimensions padded to a multiple of 16. NVIDIA's coopmat2 implementation requires multiples of 16 for N and K, and needs the matrix dimensions padded and loads clamped. Store the FA pipelines in a map, indexed by the pipeline state.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
The scalar FA shader already handled multiples of 8. The coopmat1 FA shader assumed 16x16x16 and the shared memory allocations need the HSK dimensions padded to a multiple of 16. NVIDIA's coopmat2 implementation requires multiples of 16 for N and K, and needs the matrix dimensions padded and loads clamped.
Store the FA pipelines in a map, indexed by the pipeline state.
I was looking at stable-diffusion.cpp and noticed that some models (stable diffusion 1.5) use attention head sizes that we don't support (40 and 160). Enabling FA is 2.5x faster than the full attention calculation.