[llvm] [Offload] Add olGetKernelMaxGroupSize (PR #142950)
Ross Brunton via llvm-commits
llvm-commits at lists.llvm.org
Mon Jun 30 08:36:22 PDT 2025
https://github.com/RossBrunton updated https://github.com/llvm/llvm-project/pull/142950
>From 09d5cab96ebc8a812bd385c5d2a18a64aab0ed2e Mon Sep 17 00:00:00 2001
From: Ross Brunton <ross at codeplay.com>
Date: Thu, 5 Jun 2025 12:21:52 +0100
Subject: [PATCH 1/2] [Offload] Add olKernelMaxGroupSize
This is equivalent to `cuOccupancyMaxPotentialBlockSize`. It is currently
only implented on Cuda; AMDGPU and Host return the legal-but-suboptimal
value of `1`.
Co-Authored-By: Callum Fare <callum at codeplay.com>
---
offload/liboffload/API/Kernel.td | 13 +++++++
offload/liboffload/src/OffloadImpl.cpp | 20 +++++++++-
offload/plugins-nextgen/amdgpu/src/rtl.cpp | 8 ++++
.../common/include/PluginInterface.h | 3 ++
.../cuda/dynamic_cuda/cuda.cpp | 1 +
.../plugins-nextgen/cuda/dynamic_cuda/cuda.h | 3 ++
offload/plugins-nextgen/cuda/src/rtl.cpp | 14 +++++++
offload/plugins-nextgen/host/src/rtl.cpp | 7 ++++
offload/unittests/OffloadAPI/CMakeLists.txt | 1 +
.../kernel/olGetKernelMaxGroupSize.cpp | 37 +++++++++++++++++++
10 files changed, 106 insertions(+), 1 deletion(-)
create mode 100644 offload/unittests/OffloadAPI/kernel/olGetKernelMaxGroupSize.cpp
diff --git a/offload/liboffload/API/Kernel.td b/offload/liboffload/API/Kernel.td
index 0913a036fa04f..549ef79fbea42 100644
--- a/offload/liboffload/API/Kernel.td
+++ b/offload/liboffload/API/Kernel.td
@@ -24,6 +24,19 @@ def : Function {
let returns = [];
}
+def : Function {
+ let name = "olGetKernelMaxGroupSize";
+ let desc = "Get the maximum block size needed to achieve maximum occupancy.";
+ let details = [];
+ let params = [
+ Param<"ol_kernel_handle_t", "Kernel", "handle of the kernel", PARAM_IN>,
+ Param<"ol_device_handle_t", "Device", "device intended to run the kernel", PARAM_IN>,
+ Param<"size_t", "SharedMemory", "dynamic shared memory required", PARAM_IN>,
+ Param<"size_t*", "GroupSize", "maximum block size", PARAM_OUT>
+ ];
+ let returns = [];
+}
+
def : Struct {
let name = "ol_kernel_launch_size_args_t";
let desc = "Size-related arguments for a kernel launch.";
diff --git a/offload/liboffload/src/OffloadImpl.cpp b/offload/liboffload/src/OffloadImpl.cpp
index e7da4eddce54f..329a8878ff6ec 100644
--- a/offload/liboffload/src/OffloadImpl.cpp
+++ b/offload/liboffload/src/OffloadImpl.cpp
@@ -557,6 +557,10 @@ Error olDestroyProgram_impl(ol_program_handle_t Program) {
return olDestroy(Program);
}
+inline GenericKernelTy *getPluginKernel(ol_kernel_handle_t OlKernel) {
+ return reinterpret_cast<GenericKernelTy *>(OlKernel);
+}
+
Error olGetKernel_impl(ol_program_handle_t Program, const char *KernelName,
ol_kernel_handle_t *Kernel) {
@@ -573,6 +577,20 @@ Error olGetKernel_impl(ol_program_handle_t Program, const char *KernelName,
return Error::success();
}
+Error olGetKernelMaxGroupSize_impl(ol_kernel_handle_t Kernel,
+ ol_device_handle_t Device,
+ size_t DynamicMemSize, size_t *GroupSize) {
+ auto *KernelImpl = getPluginKernel(Kernel);
+
+ auto Res = KernelImpl->maxGroupSize(*Device->Device, DynamicMemSize);
+ if (auto Err = Res.takeError())
+ return Err;
+
+ *GroupSize = *Res;
+
+ return Error::success();
+}
+
Error olLaunchKernel_impl(ol_queue_handle_t Queue, ol_device_handle_t Device,
ol_kernel_handle_t Kernel, const void *ArgumentsData,
size_t ArgumentsSize,
@@ -603,7 +621,7 @@ Error olLaunchKernel_impl(ol_queue_handle_t Queue, ol_device_handle_t Device,
// Don't do anything with pointer indirection; use arg data as-is
LaunchArgs.Flags.IsCUDA = true;
- auto *KernelImpl = reinterpret_cast<GenericKernelTy *>(Kernel);
+ auto *KernelImpl = getPluginKernel(Kernel);
auto Err = KernelImpl->launch(*DeviceImpl, LaunchArgs.ArgPtrs, nullptr,
LaunchArgs, AsyncInfoWrapper);
diff --git a/offload/plugins-nextgen/amdgpu/src/rtl.cpp b/offload/plugins-nextgen/amdgpu/src/rtl.cpp
index 35cb297f65188..4369ccb6208ed 100644
--- a/offload/plugins-nextgen/amdgpu/src/rtl.cpp
+++ b/offload/plugins-nextgen/amdgpu/src/rtl.cpp
@@ -570,6 +570,14 @@ struct AMDGPUKernelTy : public GenericKernelTy {
KernelLaunchParamsTy LaunchParams,
AsyncInfoWrapperTy &AsyncInfoWrapper) const override;
+ /// Return maximum block size for maximum occupancy
+ ///
+ /// TODO: This needs to be implemented for amdgpu
+ Expected<size_t> maxGroupSize(GenericDeviceTy &GenericDevice,
+ size_t DynamicMemSize) const override {
+ return 1;
+ }
+
/// Print more elaborate kernel launch info for AMDGPU
Error printLaunchInfoDetails(GenericDeviceTy &GenericDevice,
KernelArgsTy &KernelArgs, uint32_t NumThreads[3],
diff --git a/offload/plugins-nextgen/common/include/PluginInterface.h b/offload/plugins-nextgen/common/include/PluginInterface.h
index fbc798faec24b..753b193de65b3 100644
--- a/offload/plugins-nextgen/common/include/PluginInterface.h
+++ b/offload/plugins-nextgen/common/include/PluginInterface.h
@@ -316,6 +316,9 @@ struct GenericKernelTy {
KernelLaunchParamsTy LaunchParams,
AsyncInfoWrapperTy &AsyncInfoWrapper) const = 0;
+ virtual Expected<size_t> maxGroupSize(GenericDeviceTy &GenericDevice,
+ size_t DynamicMemSize) const = 0;
+
/// Get the kernel name.
const char *getName() const { return Name; }
diff --git a/offload/plugins-nextgen/cuda/dynamic_cuda/cuda.cpp b/offload/plugins-nextgen/cuda/dynamic_cuda/cuda.cpp
index e5332686fcffb..e6699ee78596d 100644
--- a/offload/plugins-nextgen/cuda/dynamic_cuda/cuda.cpp
+++ b/offload/plugins-nextgen/cuda/dynamic_cuda/cuda.cpp
@@ -71,6 +71,7 @@ DLWRAP(cuDevicePrimaryCtxGetState, 3)
DLWRAP(cuDevicePrimaryCtxSetFlags, 2)
DLWRAP(cuDevicePrimaryCtxRetain, 2)
DLWRAP(cuModuleLoadDataEx, 5)
+DLWRAP(cuOccupancyMaxPotentialBlockSize, 6)
DLWRAP(cuDeviceCanAccessPeer, 3)
DLWRAP(cuCtxEnablePeerAccess, 2)
diff --git a/offload/plugins-nextgen/cuda/dynamic_cuda/cuda.h b/offload/plugins-nextgen/cuda/dynamic_cuda/cuda.h
index 1c5b421768894..2c856c68a9368 100644
--- a/offload/plugins-nextgen/cuda/dynamic_cuda/cuda.h
+++ b/offload/plugins-nextgen/cuda/dynamic_cuda/cuda.h
@@ -289,6 +289,7 @@ static inline void *CU_LAUNCH_PARAM_BUFFER_POINTER = (void *)0x01;
static inline void *CU_LAUNCH_PARAM_BUFFER_SIZE = (void *)0x02;
typedef void (*CUstreamCallback)(CUstream, CUresult, void *);
+typedef size_t (*CUoccupancyB2DSize)(int);
CUresult cuCtxGetDevice(CUdevice *);
CUresult cuDeviceGet(CUdevice *, int);
@@ -370,5 +371,7 @@ CUresult cuMemSetAccess(CUdeviceptr ptr, size_t size,
CUresult cuMemGetAllocationGranularity(size_t *granularity,
const CUmemAllocationProp *prop,
CUmemAllocationGranularity_flags option);
+CUresult cuOccupancyMaxPotentialBlockSize(int *, int *, CUfunction,
+ CUoccupancyB2DSize, size_t, int);
#endif
diff --git a/offload/plugins-nextgen/cuda/src/rtl.cpp b/offload/plugins-nextgen/cuda/src/rtl.cpp
index f1164074f9ea9..f154718e91440 100644
--- a/offload/plugins-nextgen/cuda/src/rtl.cpp
+++ b/offload/plugins-nextgen/cuda/src/rtl.cpp
@@ -157,6 +157,20 @@ struct CUDAKernelTy : public GenericKernelTy {
KernelLaunchParamsTy LaunchParams,
AsyncInfoWrapperTy &AsyncInfoWrapper) const override;
+ /// Return maximum block size for maximum occupancy
+ Expected<size_t> maxGroupSize(GenericDeviceTy &,
+ size_t DynamicMemSize) const override {
+ int minGridSize;
+ int maxBlockSize;
+ auto Res = cuOccupancyMaxPotentialBlockSize(
+ &minGridSize, &maxBlockSize, Func, NULL, DynamicMemSize, INT_MAX);
+ if (auto Err = Plugin::check(
+ Res, "error in cuOccupancyMaxPotentialBlockSize: %s")) {
+ return Err;
+ }
+ return maxBlockSize;
+ }
+
private:
/// The CUDA kernel function to execute.
CUfunction Func;
diff --git a/offload/plugins-nextgen/host/src/rtl.cpp b/offload/plugins-nextgen/host/src/rtl.cpp
index a35910aece986..9d5fa153643ef 100644
--- a/offload/plugins-nextgen/host/src/rtl.cpp
+++ b/offload/plugins-nextgen/host/src/rtl.cpp
@@ -114,6 +114,13 @@ struct GenELF64KernelTy : public GenericKernelTy {
return Plugin::success();
}
+ /// Return maximum block size for maximum occupancy
+ Expected<size_t> maxGroupSize(GenericDeviceTy &Device,
+ size_t DynamicMemSize) const override {
+ // TODO
+ return 1;
+ }
+
private:
/// The kernel function to execute.
void (*Func)(void);
diff --git a/offload/unittests/OffloadAPI/CMakeLists.txt b/offload/unittests/OffloadAPI/CMakeLists.txt
index 05e862865ed33..a10822372a1c6 100644
--- a/offload/unittests/OffloadAPI/CMakeLists.txt
+++ b/offload/unittests/OffloadAPI/CMakeLists.txt
@@ -18,6 +18,7 @@ target_compile_definitions("init.unittests" PRIVATE DISABLE_WRAPPER)
add_offload_unittest("kernel"
kernel/olGetKernel.cpp
+ kernel/olGetKernelMaxGroupSize.cpp
kernel/olLaunchKernel.cpp)
add_offload_unittest("memory"
diff --git a/offload/unittests/OffloadAPI/kernel/olGetKernelMaxGroupSize.cpp b/offload/unittests/OffloadAPI/kernel/olGetKernelMaxGroupSize.cpp
new file mode 100644
index 0000000000000..f81986f535c0f
--- /dev/null
+++ b/offload/unittests/OffloadAPI/kernel/olGetKernelMaxGroupSize.cpp
@@ -0,0 +1,37 @@
+//===------- Offload API tests - olGetKernelMaxGroupSize ------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "../common/Fixtures.hpp"
+#include <OffloadAPI.h>
+#include <gtest/gtest.h>
+
+using olKernelGetMaxGroupSizeTest = OffloadKernelTest;
+OFFLOAD_TESTS_INSTANTIATE_DEVICE_FIXTURE(olKernelGetMaxGroupSizeTest);
+
+TEST_P(olKernelGetMaxGroupSizeTest, Success) {
+ size_t Size{0};
+ ASSERT_SUCCESS(olGetKernelMaxGroupSize(Kernel, Device, 0, &Size));
+ ASSERT_GT(Size, 0u);
+}
+
+TEST_P(olKernelGetMaxGroupSizeTest, NullKernel) {
+ size_t Size;
+ ASSERT_ERROR(OL_ERRC_INVALID_NULL_HANDLE,
+ olGetKernelMaxGroupSize(nullptr, Device, 0, &Size));
+}
+
+TEST_P(olKernelGetMaxGroupSizeTest, NullDevice) {
+ size_t Size;
+ ASSERT_ERROR(OL_ERRC_INVALID_NULL_HANDLE,
+ olGetKernelMaxGroupSize(Kernel, nullptr, 0, &Size));
+}
+
+TEST_P(olKernelGetMaxGroupSizeTest, NullOutput) {
+ ASSERT_ERROR(OL_ERRC_INVALID_NULL_POINTER,
+ olGetKernelMaxGroupSize(Kernel, Device, 0, nullptr));
+}
>From 1b0f3d630a0d1129c836ce1e0434ebcb24a6065f Mon Sep 17 00:00:00 2001
From: Ross Brunton <ross at codeplay.com>
Date: Mon, 30 Jun 2025 16:22:33 +0100
Subject: [PATCH 2/2] Use uint64_t rather than size_t
---
offload/plugins-nextgen/amdgpu/src/rtl.cpp | 4 ++--
offload/plugins-nextgen/common/include/PluginInterface.h | 4 ++--
offload/plugins-nextgen/cuda/src/rtl.cpp | 4 ++--
offload/plugins-nextgen/host/src/rtl.cpp | 4 ++--
4 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/offload/plugins-nextgen/amdgpu/src/rtl.cpp b/offload/plugins-nextgen/amdgpu/src/rtl.cpp
index 4369ccb6208ed..19d1c96cd1066 100644
--- a/offload/plugins-nextgen/amdgpu/src/rtl.cpp
+++ b/offload/plugins-nextgen/amdgpu/src/rtl.cpp
@@ -573,8 +573,8 @@ struct AMDGPUKernelTy : public GenericKernelTy {
/// Return maximum block size for maximum occupancy
///
/// TODO: This needs to be implemented for amdgpu
- Expected<size_t> maxGroupSize(GenericDeviceTy &GenericDevice,
- size_t DynamicMemSize) const override {
+ Expected<uint64_t> maxGroupSize(GenericDeviceTy &GenericDevice,
+ uint64_t DynamicMemSize) const override {
return 1;
}
diff --git a/offload/plugins-nextgen/common/include/PluginInterface.h b/offload/plugins-nextgen/common/include/PluginInterface.h
index 753b193de65b3..ae68f05c9ece0 100644
--- a/offload/plugins-nextgen/common/include/PluginInterface.h
+++ b/offload/plugins-nextgen/common/include/PluginInterface.h
@@ -316,8 +316,8 @@ struct GenericKernelTy {
KernelLaunchParamsTy LaunchParams,
AsyncInfoWrapperTy &AsyncInfoWrapper) const = 0;
- virtual Expected<size_t> maxGroupSize(GenericDeviceTy &GenericDevice,
- size_t DynamicMemSize) const = 0;
+ virtual Expected<uint64_t> maxGroupSize(GenericDeviceTy &GenericDevice,
+ uint64_t DynamicMemSize) const = 0;
/// Get the kernel name.
const char *getName() const { return Name; }
diff --git a/offload/plugins-nextgen/cuda/src/rtl.cpp b/offload/plugins-nextgen/cuda/src/rtl.cpp
index f154718e91440..05b165e38fefd 100644
--- a/offload/plugins-nextgen/cuda/src/rtl.cpp
+++ b/offload/plugins-nextgen/cuda/src/rtl.cpp
@@ -158,8 +158,8 @@ struct CUDAKernelTy : public GenericKernelTy {
AsyncInfoWrapperTy &AsyncInfoWrapper) const override;
/// Return maximum block size for maximum occupancy
- Expected<size_t> maxGroupSize(GenericDeviceTy &,
- size_t DynamicMemSize) const override {
+ Expected<uint64_t> maxGroupSize(GenericDeviceTy &,
+ uint64_t DynamicMemSize) const override {
int minGridSize;
int maxBlockSize;
auto Res = cuOccupancyMaxPotentialBlockSize(
diff --git a/offload/plugins-nextgen/host/src/rtl.cpp b/offload/plugins-nextgen/host/src/rtl.cpp
index 9d5fa153643ef..eb1f8782abc40 100644
--- a/offload/plugins-nextgen/host/src/rtl.cpp
+++ b/offload/plugins-nextgen/host/src/rtl.cpp
@@ -115,8 +115,8 @@ struct GenELF64KernelTy : public GenericKernelTy {
}
/// Return maximum block size for maximum occupancy
- Expected<size_t> maxGroupSize(GenericDeviceTy &Device,
- size_t DynamicMemSize) const override {
+ Expected<uint64_t> maxGroupSize(GenericDeviceTy &Device,
+ uint64_t DynamicMemSize) const override {
// TODO
return 1;
}
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