mlx/mlx/backend/cuda/jit_module.cpp
2025-06-13 19:21:46 -07:00

349 lines
10 KiB
C++

// Copyright © 2025 Apple Inc.
#include "mlx/backend/cuda/jit_module.h"
#include "mlx/backend/cuda/device.h"
#include "cuda_jit_sources.h"
#include <cstdlib>
#include <filesystem>
#include <fstream>
#include <unordered_map>
#include <fmt/format.h>
#include <nvrtc.h>
namespace mlx::core::cu {
namespace {
#define CHECK_NVRTC_ERROR(cmd) check_nvrtc_error(#cmd, (cmd))
void check_nvrtc_error(const char* name, nvrtcResult err) {
if (err != NVRTC_SUCCESS) {
throw std::runtime_error(
fmt::format("{} failed: {}", name, nvrtcGetErrorString(err)));
}
}
#define CHECK_CU_ERROR(cmd) check_cu_error(#cmd, (cmd))
void check_cu_error(const char* name, CUresult err) {
if (err != CUDA_SUCCESS) {
const char* err_str = "Unknown error";
cuGetErrorString(err, &err_str);
throw std::runtime_error(fmt::format("{} failed: {}", name, err_str));
}
}
// Return the location of the CUDA toolkit.
const char* cuda_home() {
const char* home = std::getenv("CUDA_HOME");
if (home) {
return home;
}
home = std::getenv("CUDA_PATH");
if (home) {
return home;
}
#if defined(__linux__)
home = "/usr/local/cuda";
if (std::filesystem::exists(home)) {
return home;
}
#endif
throw std::runtime_error(
"Environment variable CUDA_HOME or CUDA_PATH is not set.");
}
// Get the cache directory for storing compiled results.
bool get_ptx_cache_dir(std::filesystem::path* result) {
auto path = std::filesystem::temp_directory_path() / "mlx" / "ptx";
if (!std::filesystem::is_directory(path)) {
std::error_code error;
if (!std::filesystem::create_directories(path, error)) {
return false;
}
}
*result = path;
return true;
}
// Try to read the cached |ptx| and |ptx_kernels| from |cache_dir|.
bool read_cached_ptx(
const std::filesystem::path& cache_dir,
const std::string& module_name,
std::vector<char>* ptx,
std::vector<std::pair<std::string, std::string>>* ptx_kernels) {
auto ptx_path = cache_dir / (module_name + ".ptx");
std::error_code error;
auto ptx_size = std::filesystem::file_size(ptx_path, error);
if (error) {
return false;
}
std::ifstream ptx_file(ptx_path, std::ios::binary);
if (!ptx_file.good()) {
return false;
}
ptx->resize(ptx_size);
ptx_file.read(ptx->data(), ptx_size);
std::ifstream txt_file(cache_dir / (module_name + ".txt"), std::ios::binary);
std::string line;
while (std::getline(txt_file, line)) {
auto tab = line.find('\t');
if (tab != std::string::npos) {
ptx_kernels->emplace_back(line.substr(0, tab), line.substr(tab + 1));
}
}
return true;
}
// Write the |ptx| and |ptx_kernels| to |cache_dir| with |name|.
void write_cached_ptx(
const std::filesystem::path& cache_dir,
const std::string& module_name,
const std::vector<char>& ptx,
const std::vector<std::pair<std::string, std::string>>& ptx_kernels) {
std::ofstream ptx_file(cache_dir / (module_name + ".ptx"), std::ios::binary);
if (!ptx.empty()) {
ptx_file.write(&ptx.front(), ptx.size());
}
std::ofstream txt_file(cache_dir / (module_name + ".txt"), std::ios::binary);
for (const auto& [name, mangled] : ptx_kernels) {
txt_file << name << "\t" << mangled << std::endl;
}
}
// Return if |device|'s version is not newer than |major|.|minor| version.
inline bool version_lower_equal(Device& device, int major, int minor) {
if (device.compute_capability_major() < major) {
return true;
} else if (device.compute_capability_major() == major) {
return device.compute_capability_minor() <= minor;
} else {
return false;
}
}
// Return whether NVRTC supports compiling to |device|'s SASS code.
bool compiler_supports_device_sass(Device& device) {
int nvrtc_major, nvrtc_minor;
CHECK_NVRTC_ERROR(nvrtcVersion(&nvrtc_major, &nvrtc_minor));
if (nvrtc_major < 9) {
return false;
} else if (nvrtc_major == 9) {
return version_lower_equal(device, 7, 2);
} else if (nvrtc_major == 10) {
return version_lower_equal(device, 7, 5);
} else if (nvrtc_major == 11 && nvrtc_minor == 0) {
return version_lower_equal(device, 8, 0);
} else if (nvrtc_major == 11 && nvrtc_minor < 8) {
return version_lower_equal(device, 8, 6);
} else {
return true;
}
}
#define INCLUDE_PREFIX "mlx/backend/cuda/device/"
constexpr const char* g_include_names[] = {
INCLUDE_PREFIX "atomic_ops.cuh",
INCLUDE_PREFIX "binary_ops.cuh",
INCLUDE_PREFIX "cast_op.cuh",
INCLUDE_PREFIX "config.h",
INCLUDE_PREFIX "cucomplex_math.cuh",
INCLUDE_PREFIX "fp16_math.cuh",
INCLUDE_PREFIX "indexing.cuh",
INCLUDE_PREFIX "scatter_ops.cuh",
INCLUDE_PREFIX "unary_ops.cuh",
INCLUDE_PREFIX "ternary_ops.cuh",
INCLUDE_PREFIX "utils.cuh",
};
#undef INCLUDE_PREFIX
constexpr const char* g_headers[] = {
jit_source_atomic_ops,
jit_source_binary_ops,
jit_source_cast_op,
jit_source_config,
jit_source_cucomplex_math,
jit_source_fp16_math,
jit_source_indexing,
jit_source_scatter_ops,
jit_source_unary_ops,
jit_source_ternary_ops,
jit_source_utils,
};
} // namespace
JitModule::JitModule(
Device& device,
const std::string& module_name,
const KernelBuilder& builder) {
// Check cache.
std::filesystem::path cache_dir;
std::vector<char> ptx;
std::vector<std::pair<std::string, std::string>> ptx_kernels;
if (!get_ptx_cache_dir(&cache_dir) ||
!read_cached_ptx(cache_dir, module_name, &ptx, &ptx_kernels)) {
// Create program.
auto [source_code, kernel_names] = builder();
nvrtcProgram prog;
CHECK_NVRTC_ERROR(nvrtcCreateProgram(
&prog,
source_code.c_str(),
(module_name + ".cu").c_str(),
std::size(g_headers),
g_headers,
g_include_names));
std::unique_ptr<nvrtcProgram, void (*)(nvrtcProgram*)> prog_freer(
&prog,
[](nvrtcProgram* p) { CHECK_NVRTC_ERROR(nvrtcDestroyProgram(p)); });
for (const auto& name : kernel_names) {
CHECK_NVRTC_ERROR(nvrtcAddNameExpression(prog, name.c_str()));
}
// Compile program.
bool use_sass = compiler_supports_device_sass(device);
std::string compute = fmt::format(
"--gpu-architecture={}_{}{}",
use_sass ? "sm" : "compute",
device.compute_capability_major(),
device.compute_capability_minor());
std::string include = fmt::format("--include-path={}/include", cuda_home());
const char* args[] = {compute.c_str(), include.c_str()};
nvrtcResult compile_result =
nvrtcCompileProgram(prog, std::size(args), args);
if (compile_result != NVRTC_SUCCESS) {
size_t log_size;
CHECK_NVRTC_ERROR(nvrtcGetProgramLogSize(prog, &log_size));
std::vector<char> log(log_size + 1, 0);
CHECK_NVRTC_ERROR(nvrtcGetProgramLog(prog, log.data()));
throw std::runtime_error(
fmt::format("Failed to compile kernel: {}.", log.data()));
}
// Get mangled names of kernel names.
for (const auto& name : kernel_names) {
const char* mangled;
CHECK_NVRTC_ERROR(nvrtcGetLoweredName(prog, name.c_str(), &mangled));
ptx_kernels.emplace_back(name, mangled);
}
// Get ptx data.
size_t ptx_size;
if (use_sass) {
CHECK_NVRTC_ERROR(nvrtcGetCUBINSize(prog, &ptx_size));
} else {
CHECK_NVRTC_ERROR(nvrtcGetPTXSize(prog, &ptx_size));
}
ptx.resize(ptx_size, 0);
if (use_sass) {
CHECK_NVRTC_ERROR(nvrtcGetCUBIN(prog, ptx.data()));
} else {
CHECK_NVRTC_ERROR(nvrtcGetPTX(prog, ptx.data()));
}
write_cached_ptx(cache_dir, module_name, ptx, ptx_kernels);
}
// Load module.
char jit_log[4089] = {};
CUjit_option options[] = {
CU_JIT_ERROR_LOG_BUFFER, CU_JIT_ERROR_LOG_BUFFER_SIZE_BYTES};
void* values[] = {jit_log, reinterpret_cast<void*>(std::size(jit_log) - 1)};
CUresult jit_result = cuModuleLoadDataEx(
&module_, ptx.data(), std::size(options), options, values);
if (jit_result != CUDA_SUCCESS) {
throw std::runtime_error(fmt::format(
"Failed to load compiled {} kernel: {}.", module_name, jit_log));
}
// Load kernels.
for (const auto& [name, mangled] : ptx_kernels) {
CUfunction kernel;
CHECK_CU_ERROR(cuModuleGetFunction(&kernel, module_, mangled.c_str()));
kernels_[name] = kernel;
}
}
JitModule::~JitModule() {
CHECK_CU_ERROR(cuModuleUnload(module_));
}
void JitModule::launch_kernel(
CUstream stream,
const std::string& kernel_name,
const array& arr,
bool large,
int work_per_thread) {
CUfunction kernel = get_kernel(kernel_name);
size_t nthreads = cuda::ceil_div(arr.size(), work_per_thread);
int _, block_dim;
CHECK_CU_ERROR(
cuOccupancyMaxPotentialBlockSize(&_, &block_dim, kernel, 0, 0, 0));
if (block_dim > nthreads) {
block_dim = nthreads;
}
Dims num_blocks{1, 1, 1};
if (large) {
num_blocks =
get_2d_grid_dims_common(arr.shape(), arr.strides(), work_per_thread);
std::get<0>(num_blocks) =
(std::get<0>(num_blocks) + block_dim - 1) / block_dim;
} else {
std::get<0>(num_blocks) = (nthreads + block_dim - 1) / block_dim;
}
launch_kernel(stream, kernel, num_blocks, Dims{block_dim, 1, 1});
}
void JitModule::launch_kernel(
CUstream stream,
CUfunction kernel,
Dims num_blocks,
Dims block_dims) {
CHECK_CU_ERROR(cuLaunchKernel(
kernel,
std::get<0>(num_blocks),
std::get<1>(num_blocks),
std::get<2>(num_blocks),
std::get<0>(block_dims),
std::get<1>(block_dims),
std::get<2>(block_dims),
0,
stream,
args_.data(),
nullptr));
args_.clear();
storage_.clear();
}
CUfunction JitModule::get_kernel(const std::string& kernel_name) {
auto it = kernels_.find(kernel_name);
if (it == kernels_.end()) {
throw std::runtime_error(
fmt::format("There is no kernel named {}.", kernel_name));
}
return it->second;
}
void JitModule::append_ptr_arg(const void* v) {
args_.push_back(const_cast<void*>(v));
}
JitModule& get_jit_module(
const mlx::core::Device& device,
const std::string& name,
const KernelBuilder& builder) {
static std::unordered_map<std::string, JitModule> map;
auto it = map.find(name);
if (it == map.end()) {
it = map.try_emplace(name, cu::device(device), name, builder).first;
}
return it->second;
}
} // namespace mlx::core::cu