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mlx/mlx/backend/cuda/load.cpp
Awni Hannun df58b4133a
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[CUDA] Reduce use of managed memory (#2725)
* Use async cuda malloc managed with cuda 13

* add pool threshold

* refactor for regular cuda malloc

* load eval gpu for cuda

* remove use of cuda pool, use cuda free async

* fix

* fix

* fix

* fix

* fix + comment
2025-11-05 16:05:23 -08:00

61 lines
1.5 KiB
C++

// Copyright © 2023 Apple Inc.
#include <algorithm>
#include <utility>
#include "mlx/backend/cuda/device.h"
#include "mlx/backend/cuda/utils.h"
#include "mlx/primitives.h"
namespace {
template <const uint8_t scalar_size>
void swap_endianness(uint8_t* data_bytes, size_t N) {
struct Elem {
uint8_t bytes[scalar_size];
};
Elem* data = reinterpret_cast<Elem*>(data_bytes);
for (size_t i = 0; i < N; i++) {
for (size_t j = 0; j < (scalar_size / 2); j++) {
std::swap(data[i].bytes[j], data[i].bytes[scalar_size - j - 1]);
}
}
}
} // namespace
namespace mlx::core {
void Load::eval_gpu(const std::vector<array>& inputs, array& out) {
auto& encoder = cu::get_command_encoder(stream());
auto size = out.size();
auto nbytes = size * out.itemsize();
out.set_data(cu::malloc_async(nbytes, encoder.stream()));
auto out_ptr = malloc(nbytes);
reader_->read(static_cast<char*>(out_ptr), nbytes, offset_);
if (swap_endianness_) {
switch (out.itemsize()) {
case 2:
swap_endianness<2>(reinterpret_cast<uint8_t*>(out_ptr), size);
break;
case 4:
swap_endianness<4>(reinterpret_cast<uint8_t*>(out_ptr), size);
break;
case 8:
swap_endianness<8>(reinterpret_cast<uint8_t*>(out_ptr), size);
break;
}
}
CHECK_CUDA_ERROR(cudaMemcpyAsync(
gpu_ptr<void>(out),
out_ptr,
nbytes,
cudaMemcpyDefault,
encoder.stream()));
CHECK_CUDA_ERROR(cudaLaunchHostFunc(encoder.stream(), free, out_ptr));
}
} // namespace mlx::core