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[CK_TILE][FMHA] Optimize long-context decoding on gfx11/12 (#7500) ## Motivation Relevant issue: ROCM-22065 FMHA has less-than-optimal performance of long-context decoding (i.e. when seqlen_q = 1) on gfx11/12. This PR optimizes the splitkv pipeline and configs for such scenarios. ## Technical Details Optimizations applied in this PR: 1. use tiles with smaller M0 (16 vs 64), these tiles are used when seqlen_q <= 16 2. adapt qr_nwarp_sshuffle pipeline for gfx11, it allows to use more warps even for M0 = 16 (the qr pipeline parallelizes work between warps in M dim so with M0 = 16 it allows to use only 1 warp) 3. enable kMergeNumHeadGroupsSeqLenQ (an optimization that merges one group of heads in GQA) for all hdim values, not only 128 4. increase the number of splits (multiply by the number of head groups) if (3) is used 5. increase the number of splits for RDNAs (`multiProcessorCount` is the number of WGPs on RDNAs, not CUs, so it should be doubled to have meaning similar to CDNAs) Performance on gfx1151: | Case | develop (GB/s) | This PR (GB/s) | |:-------|-------:|-------:| | [fp16\|group\|bshd] b:1, h:32/32, s:1/45056, d:64/64 | 127.58 | 183.11 | | [fp16\|group\|bhsd] b:1, h:32/32, s:1/45056, d:64/64 | 153.64 | 215.02 | | [fp16\|group\|bshd] b:1, h:16/8, s:1/77184, d:128/128 | 120.51 | 225.76 | | [fp16\|group\|bhsd] b:1, h:16/8, s:1/77184, d:128/128 | 130.62 | 223.84 | | [fp16\|group\|bshd] b:1, h:32/32, s:1/9600, d:128/128 | 82.65 | 138.44 | | [fp16\|group\|bhsd] b:1, h:32/32, s:1/9600, d:128/128 | 105.75 | 220.45 | | [fp16\|group\|bshd] b:1, h:8/1, s:1/401024, d:256/256 | 16.27 | 187.89 | | [fp16\|group\|bhsd] b:1, h:8/1, s:1/401024, d:256/256 | 16.28 | 188.19 | ## Test Plan An additional test case is added to the exiting test. It uses seqlen_q = 1, GQA, no mask to trigger the changes ``` ninja test_ck_tile_fmha_fwd_fp16 && bin/test_ck_tile_fmha_fwd_fp16 --gtest_filter="*SplitKV* ninja test_ck_tile_fmha_fwd_bf16 && bin/test_ck_tile_fmha_fwd_bf16 --gtest_filter="*SplitKV* ``` Manual testing can be done with these commands: ``` bin/tile_example_fmha_fwd -prec=fp16 -mode=1 -page_block_size=128 -b=1 -h=32 -h_k=32 -d=64 -s=1 -s_k=$((352 * 128)) -lse=1 -mask=0 -num_splits=0 -kname=1 -v=1 bin/tile_example_fmha_fwd -prec=fp16 -mode=1 -page_block_size=128 -b=1 -h=16 -h_k=8 -d=128 -s=1 -s_k=$((603 * 128)) -lse=1 -mask=0 -num_splits=0 -kname=1 -v=1 bin/tile_example_fmha_fwd -prec=fp16 -mode=1 -page_block_size=128 -b=1 -h=32 -h_k=32 -d=128 -s=1 -s_k=$((75 * 128)) -lse=1 -mask=0 -num_splits=0 -kname=1 -v=1 bin/tile_example_fmha_fwd -prec=fp16 -mode=1 -page_block_size=128 -b=1 -h=8 -h_k=1 -d=256 -s=1 -s_k=$((3133 * 128)) -lse=1 -mask=0 -num_splits=0 -kname=1 -v=1 ``` ## Test Result All the tests must pass. ## Submission Checklist - [x] Look over the contributing guidelines at https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.
CK Tile Example Suite
This directory contains a comprehensive suite of examples demonstrating the CK Tile programming model for high-performance GPU kernels. Each example illustrates a key deep learning or HPC operation, implemented using tile-based parallelism, modular pipelines, and data movement policy.
What is CK Tile?
CK Tile is a composable GPU programming API that expresses kernels as a composition of "tiles"—rectangular blocks of computation and data movement. The pipeline & policy orchestrates data movement (global <-> LDS <-> registers), computation, and synchronization, enabling high efficiency and flexibility.
Example Index
| Example | Operation | Description |
|---|---|---|
| 01_fmha | Fused Multi-Head Attention | Tile-based FMHA with masking, quantization, and epilogue fusion |
| 02_layernorm2d | LayerNorm2D | Blockwise layer normalization with fusion and quantization |
| 03_gemm | GEMM | Matrix multiplication with tilewise parallelism |
| 04_img2col | im2col | Image-to-column transformation for GEMM-based convolution |
| 05_reduce | Reduction | Tilewise sum, max, mean reductions |
| 06_permute | Permute | Generic tensor permutation (up to rank-8) |
| 09_topk_softmax | TopK-Softmax | Rowwise softmax and top-k selection for MoE gating |
| 10_rmsnorm2d | RMSNorm2D | Root mean square normalization for LLMs |
| 11_add_rmsnorm2d_rdquant | Add + RMSNorm2D + RDQuant | Fused add, RMSNorm, and rowwise dynamic quantization |
| 12_smoothquant | SmoothQuant | Per-channel scaling and quantization for int8 inference |
| 13_moe_sorting | MoE Sorting | Token-to-expert rearrangement for MoE dispatch |
| 14_moe_smoothquant | MoE-SmoothQuant | Expert-dependent quantization fused with top-k selection |
| 15_fused_moe | Fused MoE | End-to-end fused MoE block: sorting, group-GEMM, activation, weighting |
| 16_batched_gemm | Batched GEMM | Parallel computation of multiple GEMMs |
| 17_grouped_gemm | Grouped GEMM | Multiple independent GEMMs with different shapes |
| 18_flatmm | FLATMM | Flattened matrix multiplication for packed layouts |
| 19_gemm_multi_d | Multi-D GEMM | GEMM with multiple side inputs (bias, residual, etc.) |
| 35_batched_transpose | Batched Transpose | NCHW <-> NHWC and other layout conversions |
| 36_copy | Copy | Minimal example for tile-based memory movement |
| 37_transpose | Block Transpose | High-performance tiled transpose for large tensors |
Technical Highlights
- Tile Distribution: See
include/ck_tile/tile_program/tile_distribution/for mapping tiles to thread blocks. - Block Tile Pipelines: See
include/ck_tile/tile_program/block_tile_pipeline/for memory/computation pipelines. - Policies and Utilities: Many examples use custom policies for tile/block size and memory access.
How to Build & Run
mkdir build && cd build
sh ../script/cmake-ck-dev.sh ../ <arch>
make -j
Each example produces its own executable in build/bin/.
Learning and Extending
- Start Simple: Try 03_gemm or 36_copy to learn tile basics.
- Explore Fusion: See 11_add_rmsnorm2d_rdquant, 15_fused_moe, or 14_moe_smoothquant for advanced fusion.
- Experiment: Modify tile sizes, layouts, or pipelines to explore performance and flexibility.