mirror of
https://github.com/ROCm/composable_kernel.git
synced 2026-05-14 10:09:41 +00:00
f5e00ec904
## Motivation
`qr_hpad` currently executes work for padded head-dim fragments even
when only a subset of the values are valid. This adds unnecessary
computation for head dimensions that require padding, such as `hdim=72`
and `hdim=80`, and hurts FMHA forward performance.
The goal of this PR is to make the padded-head-dim path skip invalid
work based on the actual valid fragment count, while preserving the
existing behavior for the non-padded path.
## Technical Details
This PR improves the `qr_hpad` FMHA forward path in three parts:
- Skip padded `k`/`n` fragments in the GEMM/pipeline path when only part
of the fragment is valid.
- Add partial GEMM0 tail handling for `qr_hpad` so the kernel uses the
valid fragment range instead of always computing over the padded extent.
- Retune the gfx11 `qr_hpad` kernel configuration after enabling the
partial-fragment path.
To keep the existing path stable, the implementation adds overloads for
the updated GEMM/pipeline interfaces. This allows existing full-tile
callers to keep using the previous form, while the `qr_hpad` path can
pass valid fragment counts when needed.
## Test Plan
./build/bin/tile_example_fmha_fwd -prec=bf16 -mode={0/1} -b=1 -h=16
-d={72/80} -s={seqlen} -s_k={seqlen} -lse=0 -iperm={0/1} -operm={0/1}
## Test Result
- On gfx11 and gfx12, for head dimensions that require padding,
`tile_example_fmha_fwd` shows about 20-30% performance improvement at
`hdim=72/80`.
## Submission Checklist
- [ ] Look over the contributing guidelines at
https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.