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Simplify compatibilty mode implementation
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@kingcrimsontianyu
kingcrimsontianyu committed Jan 31, 2025
1 parent ff6f841 commit e6050ce
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Showing 2 changed files with 58 additions and 46 deletions.
23 changes: 14 additions & 9 deletions cpp/include/kvikio/file_handle.hpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -47,20 +47,18 @@ class FileHandle {
int _fd_direct_on{-1};
int _fd_direct_off{-1};
bool _initialized{false};
CompatMode _compat_mode{CompatMode::AUTO};
CompatMode _compat_mode_requested{CompatMode::AUTO};
bool _is_compat_mode_preferred{true};
bool _is_compat_mode_preferred_for_async{true};
mutable std::size_t _nbytes{0}; // The size of the underlying file, zero means unknown.
CUfileHandle_t _handle{};

/**
* @brief Given a requested compatibility mode, whether it is expected to reduce to `ON` for
* asynchronous I/O.
*
* @param requested_compat_mode Requested compatibility mode.
* @return True if POSIX I/O fallback will be used; false for cuFile I/O.
* @exception std::runtime_error When the requested compatibility mode is `OFF`, but cuFile
* batch/stream library symbol is missing, or cuFile configuration file is missing.
* @brief Determine if the asynchronous I/O should be performed or not (throw exceptions)
* according to `_compat_mode_requested`, `_is_compat_mode_preferred`, and
* `_is_compat_mode_preferred_for_async`.
*/
bool is_compat_mode_preferred_for_async(CompatMode requested_compat_mode);
void validate_compat_mode_for_async();

public:
static constexpr mode_t m644 = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH;
Expand Down Expand Up @@ -463,6 +461,13 @@ class FileHandle {
* @return Boolean answer.
*/
[[nodiscard]] bool is_compat_mode_preferred_for_async() const noexcept;

/**
* @brief Returns the initially requested compatibility mode.
*
* @return The compatibility mode initially requested.
*/
CompatMode compat_mode_requested() const noexcept;
};

} // namespace kvikio
81 changes: 44 additions & 37 deletions cpp/src/file_handle.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -122,16 +122,18 @@ FileHandle::FileHandle(std::string const& file_path,
CompatMode compat_mode)
: _fd_direct_off{open_fd(file_path, flags, false, mode)},
_initialized{true},
_compat_mode{compat_mode}
_compat_mode_requested{compat_mode}
{
_is_compat_mode_preferred = defaults::is_compat_mode_preferred(_compat_mode_requested);

if (is_compat_mode_preferred()) {
return; // Nothing to do in compatibility mode
}

// Try to open the file with the O_DIRECT flag. Fall back to compatibility mode, if it fails.
auto handle_o_direct_except = [this] {
if (_compat_mode == CompatMode::AUTO) {
_compat_mode = CompatMode::ON;
if (compat_mode_requested() == CompatMode::AUTO) {
_is_compat_mode_preferred = true;
} else { // CompatMode::OFF
throw;
}
Expand All @@ -145,7 +147,7 @@ FileHandle::FileHandle(std::string const& file_path,
handle_o_direct_except();
}

if (_compat_mode == CompatMode::ON) { return; }
if (is_compat_mode_preferred()) { return; }

// Create a cuFile handle, if not in compatibility mode
CUfileDescr_t desc{}; // It is important to set to zero!
Expand All @@ -156,31 +158,41 @@ FileHandle::FileHandle(std::string const& file_path,
auto error_code = cuFileAPI::instance().HandleRegister(&_handle, &desc);
// For the AUTO mode, if the first cuFile API call fails, fall back to the compatibility
// mode.
if (_compat_mode == CompatMode::AUTO && error_code.err != CU_FILE_SUCCESS) {
_compat_mode = CompatMode::ON;
} else {
if (compat_mode_requested() == CompatMode::AUTO && error_code.err != CU_FILE_SUCCESS) {
_is_compat_mode_preferred = true;
} else { // OFF mode
CUFILE_TRY(error_code);
}

// Check cuFile async API
static bool is_extra_symbol_available = is_stream_api_available();
static bool is_config_path_empty = config_path().empty();
_is_compat_mode_preferred_for_async =
is_compat_mode_preferred() || !is_extra_symbol_available || is_config_path_empty;
}

FileHandle::FileHandle(FileHandle&& o) noexcept
: _fd_direct_on{std::exchange(o._fd_direct_on, -1)},
_fd_direct_off{std::exchange(o._fd_direct_off, -1)},
_initialized{std::exchange(o._initialized, false)},
_compat_mode{std::exchange(o._compat_mode, CompatMode::AUTO)},
_compat_mode_requested{std::exchange(o._compat_mode_requested, CompatMode::AUTO)},
_is_compat_mode_preferred{std::exchange(o._is_compat_mode_preferred, true)},
_is_compat_mode_preferred_for_async{std::exchange(o._is_compat_mode_preferred_for_async, true)},
_nbytes{std::exchange(o._nbytes, 0)},
_handle{std::exchange(o._handle, CUfileHandle_t{})}
{
}

FileHandle& FileHandle::operator=(FileHandle&& o) noexcept
{
_fd_direct_on = std::exchange(o._fd_direct_on, -1);
_fd_direct_off = std::exchange(o._fd_direct_off, -1);
_initialized = std::exchange(o._initialized, false);
_compat_mode = std::exchange(o._compat_mode, CompatMode::AUTO);
_nbytes = std::exchange(o._nbytes, 0);
_handle = std::exchange(o._handle, CUfileHandle_t{});
_fd_direct_on = std::exchange(o._fd_direct_on, -1);
_fd_direct_off = std::exchange(o._fd_direct_off, -1);
_initialized = std::exchange(o._initialized, false);
_compat_mode_requested = std::exchange(o._compat_mode_requested, CompatMode::AUTO);
_is_compat_mode_preferred = std::exchange(o._is_compat_mode_preferred, true);
_is_compat_mode_preferred_for_async = std::exchange(o._is_compat_mode_preferred_for_async, true);
_nbytes = std::exchange(o._nbytes, 0);
_handle = std::exchange(o._handle, CUfileHandle_t{});
return *this;
}

Expand All @@ -194,7 +206,9 @@ void FileHandle::close() noexcept
if (closed()) { return; }

if (!is_compat_mode_preferred()) { cuFileAPI::instance().HandleDeregister(_handle); }
_compat_mode = CompatMode::AUTO;
_compat_mode_requested = CompatMode::AUTO;
_is_compat_mode_preferred = true;
_is_compat_mode_preferred_for_async = true;
::close(_fd_direct_off);
if (_fd_direct_on != -1) { ::close(_fd_direct_on); }
_fd_direct_on = -1;
Expand Down Expand Up @@ -375,7 +389,8 @@ void FileHandle::read_async(void* devPtr_base,
ssize_t* bytes_read_p,
CUstream stream)
{
if (is_compat_mode_preferred_for_async(_compat_mode)) {
validate_compat_mode_for_async();
if (is_compat_mode_preferred_for_async()) {
CUDA_DRIVER_TRY(cudaAPI::instance().StreamSynchronize(stream));
*bytes_read_p =
static_cast<ssize_t>(read(devPtr_base, *size_p, *file_offset_p, *devPtr_offset_p));
Expand All @@ -402,7 +417,8 @@ void FileHandle::write_async(void* devPtr_base,
ssize_t* bytes_written_p,
CUstream stream)
{
if (is_compat_mode_preferred_for_async(_compat_mode)) {
validate_compat_mode_for_async();
if (is_compat_mode_preferred_for_async()) {
CUDA_DRIVER_TRY(cudaAPI::instance().StreamSynchronize(stream));
*bytes_written_p =
static_cast<ssize_t>(write(devPtr_base, *size_p, *file_offset_p, *devPtr_offset_p));
Expand All @@ -422,34 +438,25 @@ StreamFuture FileHandle::write_async(
return ret;
}

bool FileHandle::is_compat_mode_preferred() const noexcept
{
return defaults::is_compat_mode_preferred(_compat_mode);
}
CompatMode FileHandle::compat_mode_requested() const noexcept { return _compat_mode_requested; }

bool FileHandle::is_compat_mode_preferred() const noexcept { return _is_compat_mode_preferred; }

bool FileHandle::is_compat_mode_preferred_for_async() const noexcept
{
static bool is_extra_symbol_available = is_stream_api_available();
static bool is_config_path_empty = config_path().empty();
return is_compat_mode_preferred() || !is_extra_symbol_available || is_config_path_empty;
return _is_compat_mode_preferred_for_async;
}

bool FileHandle::is_compat_mode_preferred_for_async(CompatMode requested_compat_mode)
void FileHandle::validate_compat_mode_for_async()
{
if (defaults::is_compat_mode_preferred(requested_compat_mode)) { return true; }

if (!is_stream_api_available()) {
if (requested_compat_mode == CompatMode::AUTO) { return true; }
throw std::runtime_error("Missing the cuFile stream api.");
}
if (!is_compat_mode_preferred() && is_compat_mode_preferred_for_async() &&
compat_mode_requested() == CompatMode::OFF) {
if (!is_stream_api_available()) { throw std::runtime_error("Missing the cuFile stream api."); }

// When checking for availability, we also check if cuFile's config file exists. This is
// because even when the stream API is available, it doesn't work if no config file exists.
if (config_path().empty()) {
if (requested_compat_mode == CompatMode::AUTO) { return true; }
throw std::runtime_error("Missing cuFile configuration file.");
// When checking for availability, we also check if cuFile's config file exists. This is
// because even when the stream API is available, it doesn't work if no config file exists.
if (config_path().empty()) { throw std::runtime_error("Missing cuFile configuration file."); }
}
return false;
}

} // namespace kvikio

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