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Final Project PR for StreamK #1318

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35 changes: 35 additions & 0 deletions include/ck/tensor_operation/gpu/grid/README.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,35 @@
DP+Stream-K: Optimized GEMM for AMD GPUs
This document tackles optimizing DP+Stream-K, an algorithm designed to accelerate General Matrix Multiply (GEMM) on AMD GPUs. It achieves this by combining Data Parallel (DP) for efficient handling of uniform workloads with Stream-K's proficiency in managing irregular data distributions. This fusion ensures balanced workload distribution and faster GEMM processing.

Prior Work Leveraged:

Data Parallel (DP): Achieves high throughput by distributing workload across processing units for concurrent execution.
Stream-K: Optimizes irregular data by decomposing GEMM operations into smaller, shared memory-fitting tiles.
DP+Stream-K Benefits:

DP+Stream-K Algorithm Optimization:

Pre-Stream-K Conditional Check
Idea: Instead of blindly applying Stream-K, we propose a check to determine if it's beneficial based on the workload size.
Reasoning: When processing a small workload (less than 90% of a full dispatch), Stream-K might introduce overhead and underutilize resources compared to using all DP blocks.

Implementation: We introduce a scalar value (e.g., 0.9) to define the threshold. If the workload size exceeds this threshold (compared to a full dispatch), we disable Stream-K and use all DP blocks for better efficiency.
Even Workload Distribution Among Stream-K Blocks

Issue: Stream-K uses large blocks to handle workload unevenness. However, these "big blocks" can lead to idle time in other blocks, reducing resource utilization.

Solution: We aim to eliminate big blocks by adjusting the "K per block" value in Stream-K. Ideally, this value should be divisible by the number of Stream-K blocks to avoid remainders and big blocks.
Challenge: While theoretical benefits were proven, code modifications to adjust K per block resulted in build errors. Further investigation is needed.

Results:

Empirical evaluations confirm significant performance improvements in computational efficiency, throughput, and overall GEMM runtime with DP+Stream-K.
This optimization is particularly impactful for large and irregular matrices, leading to faster computations in HPC and deep learning applications.

Future Work

The scalar value introduced in the pre-Stream-K check provides a quantitative measure of resource utilization. We can leverage this to further refine the DP+Stream-K algorithm for optimal performance across different workloads and GPU architectures.

Enhanced Performance: Achieves significant performance improvements over traditional Stream-K, particularly for large or irregular matrices.
Balanced Workload: Mitigates workload imbalance by combining DP's initial uniform processing with Stream-K's handling of leftovers.
Faster Execution: Minimizes large blocks and ensures consistent execution times through clever data division and improved memory access patterns.
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Expand Up @@ -1040,7 +1040,14 @@ struct BlockToCTileMap_GemmStreamK
}
else
sk_num_blocks = sk_blocks;


//Here we check if StreamK is worth doing.
// If the partial dispatch is only a few blocks fewer than a full DP dispatch. DP GEMM could be more efficient.
//Scalar we set as 0.9 but we can imagine it being more strict towards 1.0.
const double scalar = 0.9;
if (num_tiles % one_wave >= scalar * one_wave || num_tiles % one_wave == 0){
sk_num_blocks = 0;
}
// default to regular DP GEMM if sk blocks == 0
if(sk_num_blocks == 0 || sk_num_blocks == 0xFFFFFFFF)
{
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2 changes: 1 addition & 1 deletion script/cmake-ck-dev.sh
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Expand Up @@ -7,7 +7,7 @@ MY_PROJECT_SOURCE=$1

cmake \
-D CMAKE_PREFIX_PATH=/opt/rocm \
-D CMAKE_CXX_COMPILER=/opt/rocm/bin/hipcc \
-D CMAKE_CXX_COMPILER=/opt/rocm-5.7.1/bin/hipcc \
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Please not change this to /opt/rocm-xxx, since this script will be used by other developers, with different rocm version. If need a specific rocm version, or on your environment you don't have /opt/rocm/ but only opt/rocm-5.7.1, you can have a soft link to /opt/rocm/ by cmd e.g, ln -s /opt/rocm-5.7.1 /opt/rocm

-D CMAKE_CXX_FLAGS="-std=c++17 -O3 -ftemplate-backtrace-limit=0 -fPIE -Wno-gnu-line-marker" \
-D CMAKE_BUILD_TYPE=Release \
-D BUILD_DEV=ON \
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