[backend] add backend option to async file writer

Author: botbw

csrc/async_file_io.cpp

@@ -1,20 +1,8 @@
 #include "async_file_io.h"
 #include "backend.h"
 #include <stdexcept>
-#include <string>
 
-AsyncFileWriter::AsyncFileWriter(int fd, unsigned int n_entries) : fd(fd)
-{
-    for (const std::string &backend : get_backends())
-    {
-        if (probe_backend(backend))
-        {
-            this->aio = create_asyncio(n_entries, backend);
-            return;
-        }
-    }
-    throw std::runtime_error("No asyncio backend is installed");
-}
+AsyncFileWriter::AsyncFileWriter(int fd, unsigned int n_entries, const std::string &backend) : fd(fd), aio(create_asyncio(n_entries, backend)) {}
 
 void AsyncFileWriter::write(size_t buffer, size_t n_bytes, unsigned long long offset)
 {

csrc/backend.cpp

@@ -130,19 +130,23 @@ std::string get_default_backend() {
 AsyncIO *create_asyncio(unsigned int n_entries, std::string backend)
 {
     std::unordered_set<std::string> backends = get_backends();
+    std::string default_backend = get_default_backend();
+
     if (backends.empty())
         throw std::runtime_error("No asyncio backend is installed");
 
-    std::string default_backend = get_default_backend();
-    if (default_backend.size() > 0) {
-        std::cout << "[backend] backend is overwritten by environ TENSORNVME_BACKEND from " << backend << std::endl;
+    if (default_backend.size() > 0) {  // priority 1: environ is set
+        std::cout << "[backend] backend is overwritten by environ TENSORNVME_BACKEND from " << backend << " to " << default_backend << std::endl;
         backend = default_backend;
+    } else if (backend.size() > 0) {  // priority 2: backend is set
+        if (backends.find(backend) == backends.end())
+            throw std::runtime_error("Unsupported backend: " + backend);
     }
     std::cout << "[backend] using backend: " << backend << std::endl;
-    if (backends.find(backend) == backends.end())
-        throw std::runtime_error("Unsupported backend: " + backend);
+
     if (!probe_backend(backend))
         throw std::runtime_error("Backend \"" + backend + "\" is not install correctly");
+
 #ifndef DISABLE_URING
     if (backend == "uring")
         return new UringAsyncIO(n_entries);

csrc/py_api.cpp

@@ -12,7 +12,7 @@ namespace py = pybind11;
 PYBIND11_MODULE(TORCH_EXTENSION_NAME, m)
 {
     py::class_<Offloader>(m, "Offloader")
-        .def(py::init<const std::string &, unsigned int, const std::string &>(), py::arg("filename"), py::arg("n_entries"), py::arg("backend") = "uring")
+        .def(py::init<const std::string &, unsigned int, const std::string &>(), py::arg("filename"), py::arg("n_entries"), py::arg("backend") = "aio")
         .def("async_write", &Offloader::async_write, py::arg("tensor"), py::arg("key"), py::arg("callback") = py::none())
         .def("async_read", &Offloader::async_read, py::arg("tensor"), py::arg("key"), py::arg("callback") = py::none())
         .def("sync_write", &Offloader::sync_write, py::arg("tensor"), py::arg("key"))
@@ -27,7 +27,7 @@ PYBIND11_MODULE(TORCH_EXTENSION_NAME, m)
     m.def("get_backends", get_backends);
     m.def("probe_backend", probe_backend, py::arg("backend"));
     py::class_<AsyncFileWriter>(m, "AsyncFileWriter")
-        .def(py::init<int, unsigned int>(), py::arg("fd"), py::arg("n_entries"))
+        .def(py::init<int, unsigned int, const std::string &>(), py::arg("fd"), py::arg("n_entries"), py::arg("backend") = "aio")
         .def("write", &AsyncFileWriter::write, py::arg("buffer"), py::arg("n_bytes"), py::arg("offset"))
         .def("synchronize", &AsyncFileWriter::synchronize);
 }

include/async_file_io.h

@@ -1,4 +1,5 @@
 #pragma once
+#include <string>
 #include "asyncio.h"
 #ifndef DISABLE_URING
 #include "uring.h"
@@ -10,7 +11,7 @@
 class AsyncFileWriter
 {
 public:
-    AsyncFileWriter(int fd, unsigned int n_entries);
+    AsyncFileWriter(int fd, unsigned int n_entries, const std::string &backend);
     void write(size_t buffer, size_t n_bytes, unsigned long long offset);
     void synchronize();
     ~AsyncFileWriter();

include/offload.h

@@ -14,7 +14,7 @@
 class Offloader
 {
 public:
-    Offloader(const std::string &filename, unsigned int n_entries, const std::string &backend = "uring");
+    Offloader(const std::string &filename, unsigned int n_entries, const std::string &backend);
     SpaceInfo prepare_write(const at::Tensor &tensor, const std::string &key);
     SpaceInfo prepare_read(const at::Tensor &tensor, const std::string &key);
     void async_write(const at::Tensor &tensor, const std::string &key, callback_t callback = nullptr);

tensornvme/_C/__init__.pyi

@@ -3,7 +3,7 @@ from typing import Callable, List, Optional, Set
 from torch import Tensor
 
 class Offloader:
-    def __init__(self, filename: str, n_entries: int, backend: str = "uring") -> None: ...
+    def __init__(self, filename: str, n_entries: int, backend: str = "aio") -> None: ...
     def async_write(self, tensor: Tensor, key: str, callback: Optional[Callable[[], None]] = None) -> None: ...
     def async_read(self, tensor: Tensor, key: str, callback: Optional[Callable[[], None]] = None) -> None: ...
     def sync_write(self, tensor: Tensor, key: str) -> None: ...
@@ -20,6 +20,6 @@ def get_backends() -> Set[str]: ...
 def probe_backend(backend: str) -> bool: ...
 
 class AsyncFileWriter:
-    def __init__(self, fd: int, n_entries: int) -> None: ...
+    def __init__(self, fd: int, n_entries: int, backend: str = "aio") -> None: ...
     def write(self, buffer, n_bytes: int, offset: int) -> None: ...
     def synchronize(self) -> None: ...

tensornvme/async_file_io.py

@@ -5,9 +5,12 @@
 
 
 class AsyncFileWriter:
-    def __init__(self, fp: IOBase, n_entries: int = 16) -> None:
+    def __init__(self, fp: IOBase, n_entries: int = 16, backend=None) -> None:
         fd = fp.fileno()
-        self.io = AsyncFileWriterC(fd, n_entries)
+        if backend is not None:
+            self.io = AsyncFileWriterC(fd, n_entries, backend=backend)
+        else:
+            self.io = AsyncFileWriterC(fd, n_entries)
         self.fp = fp
         self.offset = 0
         # must ensure the data is not garbage collected