[Attention] MLA - cutlass decode with unresticted num_heads

Author: alexm-redhat

CMakeLists.txt

@@ -563,7 +563,8 @@ if(VLLM_GPU_LANG STREQUAL "CUDA")
   cuda_archs_loose_intersection(MLA_ARCHS "10.0a" "${CUDA_ARCHS}")
   if(${CMAKE_CUDA_COMPILER_VERSION} VERSION_GREATER_EQUAL 12.8 AND MLA_ARCHS)
     set(SRCS
-      "csrc/attention/mla/cutlass_mla_kernels.cu")
+      "csrc/attention/mla/cutlass_mla_kernels.cu"
+      "csrc/attention/mla/sm100_cutlass_mla_kernel.cu")
     set_gencode_flags_for_srcs(
       SRCS "${SRCS}"
       CUDA_ARCHS "${MLA_ARCHS}")

csrc/attention/mla/cutlass_sm100_mla/device/sm100_mla.hpp

@@ -0,0 +1,364 @@
+/***************************************************************************************************
+ * Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ *ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ *LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ *CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ *SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ *INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ *CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ *ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ *POSSIBILITY OF SUCH DAMAGE.
+ *
+ **************************************************************************************************/
+/*
+ * Taken from SGLANG PR https://github.com/sgl-project/sglang/pull/6929
+ * by Alcanderian JieXin Liang
+ */
+
+/*!
+ \file
+ \brief An universal device layer for cutlass 3.x-style kernels.
+*/
+
+// clang-format off
+#pragma once
+
+// common
+#include "cutlass/cutlass.h"
+#include "cutlass/device_kernel.h"
+
+#if !defined(__CUDACC_RTC__)
+#include "cutlass/cluster_launch.hpp"
+#include "cutlass/trace.h"
+#endif // !defined(__CUDACC_RTC__)
+
+#include "../kernel/sm100_fmha_mla_tma_warpspecialized.hpp"
+#include "../kernel/sm100_fmha_mla_reduction.hpp"
+
+////////////////////////////////////////////////////////////////////////////////
+
+namespace cutlass::fmha::device {
+
+using namespace cute;
+using namespace cutlass::fmha::kernel;
+
+
+////////////////////////////////////////////////////////////////////////////////
+////////////////////////////// CUTLASS 3.x API /////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+
+template<
+    class Kernel_
+>
+class MLA {
+public:
+
+  using Kernel = Kernel_;
+
+  using ReductionKernel = cutlass::fmha::kernel::Sm100FmhaMlaReductionKernel<
+      typename Kernel::ElementOut,
+      typename Kernel::ElementAcc,
+      typename Kernel::ElementAcc,
+      Kernel::TileShapeH::value,
+      Kernel::TileShapeL::value,
+      256 /*Max split*/
+  >;
+
+  /// Argument structure: User API
+  using KernelArguments = typename Kernel::Arguments;
+  using ReductionArguments = typename ReductionKernel::Arguments;
+
+  using Arguments = KernelArguments;
+
+  /// Argument structure: Kernel API
+  using KernelParams = typename Kernel::Params;
+  using ReductionParams = typename ReductionKernel::Params;
+  struct Params {
+    KernelParams fmha_params;
+    ReductionParams reduction_params;
+  };
+
+private:
+
+  /// Kernel API parameters object
+  Params params_;
+
+  bool is_initialized(bool set = false) {
+    static bool initialized = false;
+    if (set) initialized = true;
+    return initialized;
+  }
+
+  static ReductionArguments to_reduction_args(Arguments const& args) {
+    auto [H, K, D, B] = args.problem_shape;
+    return ReductionArguments{
+      nullptr, args.epilogue.ptr_o, nullptr, args.epilogue.ptr_lse,
+      args.mainloop.softmax_scale, B, args.split_kv, K, args.mainloop.ptr_seq,
+      args.ptr_split_kv, Kernel::TileShapeS::value
+    };
+  }
+
+public:
+
+  /// Access the Params structure
+  Params const& params() const {
+    return params_;
+  }
+
+  static void set_split_kv (KernelArguments& args) {
+    if (args.split_kv >= 1) return;
+    auto [H, K, D, B] = args.problem_shape;
+    int sm_count = args.hw_info.sm_count;
+    int max_splits = ceil_div(K, 128);
+    int sms_per_batch = max(1, sm_count / B);
+    int split_heur = min(max_splits, sms_per_batch);
+    int waves = ceil_div(B * split_heur, sm_count);
+    int k_waves = ceil_div(max_splits, split_heur);
+    int split_wave_aware = ceil_div(max_splits, k_waves);
+    args.split_kv = split_wave_aware;
+  }
+
+  /// Determines whether the GEMM can execute the given problem.
+  static Status
+  can_implement(Arguments const& args) {
+    if (! Kernel::can_implement(args)) {
+      return Status::kInvalid;
+    }
+    if (! ReductionKernel::can_implement(to_reduction_args(args))) {
+      return Status::kInvalid;
+    }
+    return Status::kSuccess;
+  }
+
+  /// Gets the workspace size
+  static size_t
+  get_workspace_size(Arguments const& args) {
+    size_t workspace_bytes = 0;
+    workspace_bytes += Kernel::get_workspace_size(args);
+    workspace_bytes += ReductionKernel::get_workspace_size(to_reduction_args(args));
+    return workspace_bytes;
+  }
+
+  /// Computes the maximum number of active blocks per multiprocessor
+  static int maximum_active_blocks(int /* smem_capacity */ = -1) {
+    CUTLASS_TRACE_HOST("MLA::maximum_active_blocks()");
+    int max_active_blocks = -1;
+    int smem_size = Kernel::SharedStorageSize;
+
+    // first, account for dynamic smem capacity if needed
+    cudaError_t result;
+    if (smem_size >= (48 << 10)) {
+      CUTLASS_TRACE_HOST("  Setting smem size to " << smem_size);
+      result = cudaFuncSetAttribute(
+          device_kernel<Kernel>,
+          cudaFuncAttributeMaxDynamicSharedMemorySize,
+          smem_size);
+      if (cudaSuccess != result) {
+        result = cudaGetLastError(); // to clear the error bit
+        CUTLASS_TRACE_HOST(
+          "  cudaFuncSetAttribute() returned error: "
+          << cudaGetErrorString(result));
+        return -1;
+      }
+    }
+
+    // query occupancy after setting smem size
+    result = cudaOccupancyMaxActiveBlocksPerMultiprocessor(
+        &max_active_blocks,
+        device_kernel<Kernel>,
+        Kernel::MaxThreadsPerBlock,
+        smem_size);
+
+    if (cudaSuccess != result) {
+      result = cudaGetLastError(); // to clear the error bit
+      CUTLASS_TRACE_HOST(
+        "  cudaOccupancyMaxActiveBlocksPerMultiprocessor() returned error: "
+        << cudaGetErrorString(result));
+      return -1;
+    }
+
+    CUTLASS_TRACE_HOST("  max_active_blocks: " << max_active_blocks);
+    return max_active_blocks;
+  }
+
+  /// Initializes GEMM state from arguments.
+  Status
+  initialize(Arguments const& args, void* workspace = nullptr, cudaStream_t stream = nullptr) {
+    CUTLASS_TRACE_HOST("MLA::initialize() - workspace "
+      << workspace << ", stream: " << (stream ? "non-null" : "null"));
+
+    // Initialize the workspace
+    Status status = Kernel::initialize_workspace(args, workspace, stream);
+    if (status != Status::kSuccess) {
+      return status;
+    }
+    status = ReductionKernel::initialize_workspace(to_reduction_args(args), workspace, stream);
+    if (status != Status::kSuccess) {
+      return status;
+    }
+    KernelParams kernel_params = Kernel::to_underlying_arguments(args, workspace);
+
+    ReductionArguments reduction_args = to_reduction_args(args);
+    if (reduction_args.split_kv > 1) {
+      reduction_args.ptr_oaccum   = kernel_params.epilogue.ptr_o_acc;
+      reduction_args.ptr_lseaccum = kernel_params.epilogue.ptr_lse_acc;
+    }
+    ReductionParams reduction_params = ReductionKernel::to_underlying_arguments(reduction_args, workspace);
+    // Initialize the Params structure
+    params_ = Params {kernel_params, reduction_params};
+
+    if (is_initialized()) return Status::kSuccess;
+
+    // account for dynamic smem capacity if needed
+    // no dynamic smem is needed for reduction kernel
+    int smem_size = Kernel::SharedStorageSize;
+    if (smem_size >= (48 << 10)) {
+      CUTLASS_TRACE_HOST("  Setting smem size to " << smem_size);
+      cudaError_t result = cudaFuncSetAttribute(
+          device_kernel<Kernel>,
+          cudaFuncAttributeMaxDynamicSharedMemorySize,
+          smem_size);
+      if (cudaSuccess != result) {
+        result = cudaGetLastError(); // to clear the error bit
+        CUTLASS_TRACE_HOST("  cudaFuncSetAttribute() returned error: " << cudaGetErrorString(result));
+        return Status::kErrorInternal;
+      }
+    }
+
+    is_initialized(true);
+
+    return Status::kSuccess;
+  }
+
+  /// Update API is preserved in 3.0, but does not guarantee a lightweight update of params.
+  Status
+  update(Arguments const& args, void* workspace = nullptr) {
+    CUTLASS_TRACE_HOST("MLA()::update() - workspace: " << workspace);
+
+    size_t workspace_bytes = get_workspace_size(args);
+    if (workspace_bytes > 0 && nullptr == workspace) {
+      return Status::kErrorWorkspaceNull;
+    }
+
+    auto fmha_params = Kernel::to_underlying_arguments(args, workspace);
+
+    ReductionArguments reduction_args = to_reduction_args(args);
+    if (reduction_args.split_kv > 1) {
+      reduction_args.ptr_oaccum   = fmha_params.epilogue.ptr_o_acc;
+      reduction_args.ptr_lseaccum = fmha_params.epilogue.ptr_lse_acc;
+    }
+    ReductionParams reduction_params = ReductionKernel::to_underlying_arguments(reduction_args, workspace);
+    // Initialize the Params structure
+    params_ = Params {fmha_params, reduction_params};
+
+    return Status::kSuccess;
+  }
+
+  /// Primary run() entry point API that is static allowing users to create and manage their own params.
+  /// Supplied params struct must be construct by calling Kernel::to_underling_arguments()
+  static Status
+  run(Params& params, cudaStream_t stream = nullptr) {
+    CUTLASS_TRACE_HOST("MLA::run()");
+    dim3 const block = Kernel::get_block_shape();
+    dim3 const grid = Kernel::get_grid_shape(params.fmha_params);
+
+    // configure smem size and carveout
+    int smem_size = Kernel::SharedStorageSize;
+
+    Status launch_result;
+    // Use extended launch API only for mainloops that use it
+    if constexpr(Kernel::ArchTag::kMinComputeCapability >= 90) {
+      dim3 cluster(cute::size<0>(typename Kernel::ClusterShape{}),
+                   cute::size<1>(typename Kernel::ClusterShape{}),
+                   cute::size<2>(typename Kernel::ClusterShape{}));
+      void const* kernel = (void const*) device_kernel<Kernel>;
+      void* kernel_params[] = {&params.fmha_params};
+      launch_result = ClusterLauncher::launch(grid, cluster, block, smem_size, stream, kernel, kernel_params);
+    }
+    else {
+      launch_result = Status::kSuccess;
+      device_kernel<Kernel><<<grid, block, smem_size, stream>>>(params.fmha_params);
+    }
+
+    cudaError_t result = cudaGetLastError();
+    if (cudaSuccess != result or Status::kSuccess != launch_result) {
+      //return Status::kSuccess;
+      CUTLASS_TRACE_HOST("  Kernel launch failed. Reason: " << result);
+      return Status::kErrorInternal;
+    }
+    if (params.reduction_params.split_kv > 1) {
+      // launch reduction kernel
+      dim3 const block = ReductionKernel::get_block_shape();
+      dim3 const grid  = ReductionKernel::get_grid_shape(params.reduction_params);
+      device_kernel<ReductionKernel><<<grid, block, 0, stream>>>(params.reduction_params);
+      cudaError_t result = cudaGetLastError();
+      if (cudaSuccess == result) {
+        return Status::kSuccess;
+      }
+      else {
+        CUTLASS_TRACE_HOST("  Kernel launch failed. Reason: " << result);
+        return Status::kErrorInternal;
+      }
+    }
+    else {
+      return Status::kSuccess;
+    }
+  }
+
+  //
+  // Non-static launch overloads that first create and set the internal params struct of this kernel handle.
+  //
+
+  /// Launches the kernel after first constructing Params internal state from supplied arguments.
+  Status
+  run(Arguments const& args, void* workspace = nullptr, cudaStream_t stream = nullptr) {
+    Status status = initialize(args, workspace, stream);
+    if (Status::kSuccess == status) {
+      status = run(params_, stream);
+    }
+    return status;
+  }
+
+  /// Launches the kernel after first constructing Params internal state from supplied arguments.
+  Status
+  operator()(Arguments const& args, void* workspace = nullptr, cudaStream_t stream = nullptr) {
+    return run(args, workspace, stream);
+  }
+
+  /// Overload that allows a user to re-launch the same kernel without updating internal params struct.
+  Status
+  run(cudaStream_t stream = nullptr) {
+    return run(params_, stream);
+  }
+
+  /// Overload that allows a user to re-launch the same kernel without updating internal params struct.
+  Status
+  operator()(cudaStream_t stream = nullptr) {
+    return run(params_, stream);
+  }
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
+} // namespace cutlass::fmha::device
+
+////////////////////////////////////////////////////////////////////////////////