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#include <Disks/IO/createReadBufferFromFileBase.h>
#include <IO/ReadBufferFromEmptyFile.h>
#include <IO/ReadBufferFromFile.h>
#include <IO/MMapReadBufferFromFileWithCache.h>
#include <IO/AsynchronousReadBufferFromFile.h>
#include <Disks/IO/IOUringReader.h>
#include <Disks/IO/ThreadPoolReader.h>
#include <Disks/IO/getThreadPoolReader.h>
#include <IO/SynchronousReader.h>
#include <IO/AsynchronousReader.h>
#include <Common/ProfileEvents.h>
#include "clickhouse_config.h"
namespace ProfileEvents
{
extern const Event CreatedReadBufferOrdinary;
extern const Event CreatedReadBufferDirectIO;
extern const Event CreatedReadBufferDirectIOFailed;
extern const Event CreatedReadBufferMMap;
extern const Event CreatedReadBufferMMapFailed;
}
namespace DB
{
namespace ErrorCodes
{
extern const int LOGICAL_ERROR;
extern const int UNSUPPORTED_METHOD;
}
std::unique_ptr<ReadBufferFromFileBase> createReadBufferFromFileBase(
const std::string & filename,
const ReadSettings & settings,
std::optional<size_t> read_hint,
std::optional<size_t> file_size,
int flags,
char * existing_memory,
size_t alignment)
{
if (file_size.has_value() && !*file_size)
return std::make_unique<ReadBufferFromEmptyFile>();
size_t estimated_size = 0;
if (read_hint.has_value())
estimated_size = *read_hint;
else if (file_size.has_value())
estimated_size = *file_size;
if (!existing_memory
&& settings.local_fs_method == LocalFSReadMethod::mmap
&& settings.mmap_threshold
&& settings.mmap_cache
&& estimated_size >= settings.mmap_threshold)
{
try
{
std::unique_ptr<MMapReadBufferFromFileWithCache> res;
if (file_size)
res = std::make_unique<MMapReadBufferFromFileWithCache>(*settings.mmap_cache, filename, 0, *file_size);
else
res = std::make_unique<MMapReadBufferFromFileWithCache>(*settings.mmap_cache, filename, 0);
ProfileEvents::increment(ProfileEvents::CreatedReadBufferMMap);
return res;
}
catch (const ErrnoException &)
{
/// Fallback if mmap is not supported (example: pipe).
ProfileEvents::increment(ProfileEvents::CreatedReadBufferMMapFailed);
}
}
auto create = [&](size_t buffer_size, size_t buffer_alignment, int actual_flags)
{
std::unique_ptr<ReadBufferFromFileBase> res;
if (settings.local_fs_method == LocalFSReadMethod::read)
{
res = std::make_unique<ReadBufferFromFile>(
filename,
buffer_size,
actual_flags,
existing_memory,
buffer_alignment,
file_size,
settings.local_throttler);
}
else if (settings.local_fs_method == LocalFSReadMethod::pread || settings.local_fs_method == LocalFSReadMethod::mmap)
{
res = std::make_unique<ReadBufferFromFilePReadWithDescriptorsCache>(
filename,
buffer_size,
actual_flags,
existing_memory,
buffer_alignment,
file_size,
settings.local_throttler);
}
else if (settings.local_fs_method == LocalFSReadMethod::io_uring)
{
#if USE_LIBURING
static std::shared_ptr<IOUringReader> reader = std::make_shared<IOUringReader>(512);
if (!reader->isSupported())
throw Exception(ErrorCodes::UNSUPPORTED_METHOD, "io_uring is not supported by this system");
res = std::make_unique<AsynchronousReadBufferFromFileWithDescriptorsCache>(
*reader,
settings.priority,
filename,
buffer_size,
actual_flags,
existing_memory,
buffer_alignment,
file_size,
settings.local_throttler);
#else
throw Exception(ErrorCodes::UNSUPPORTED_METHOD, "Read method io_uring is only supported in Linux");
#endif
}
else if (settings.local_fs_method == LocalFSReadMethod::pread_fake_async)
{
auto & reader = getThreadPoolReader(FilesystemReaderType::SYNCHRONOUS_LOCAL_FS_READER);
res = std::make_unique<AsynchronousReadBufferFromFileWithDescriptorsCache>(
reader,
settings.priority,
filename,
buffer_size,
actual_flags,
existing_memory,
buffer_alignment,
file_size,
settings.local_throttler);
}
else if (settings.local_fs_method == LocalFSReadMethod::pread_threadpool)
{
auto & reader = getThreadPoolReader(FilesystemReaderType::ASYNCHRONOUS_LOCAL_FS_READER);
res = std::make_unique<AsynchronousReadBufferFromFileWithDescriptorsCache>(
reader,
settings.priority,
filename,
buffer_size,
actual_flags,
existing_memory,
buffer_alignment,
file_size,
settings.local_throttler);
}
else
throw Exception(ErrorCodes::LOGICAL_ERROR, "Unknown read method");
return res;
};
if (flags == -1)
flags = O_RDONLY | O_CLOEXEC;
#if defined(OS_LINUX) || defined(OS_FREEBSD)
if (settings.direct_io_threshold && estimated_size >= settings.direct_io_threshold)
{
/** O_DIRECT
* The O_DIRECT flag may impose alignment restrictions on the length and address of user-space buffers and the file offset of I/Os.
* In Linux alignment restrictions vary by filesystem and kernel version and might be absent entirely.
* However there is currently no filesystem-independent interface for an application to discover these restrictions
* for a given file or filesystem. Some filesystems provide their own interfaces for doing so, for example the
* XFS_IOC_DIOINFO operation in xfsctl(3).
*
* Under Linux 2.4, transfer sizes, and the alignment of the user buffer and the file offset must all be
* multiples of the logical block size of the filesystem. Since Linux 2.6.0, alignment to the logical block size
* of the underlying storage (typically 512 bytes) suffices.
*
* - man 2 open
*/
constexpr size_t min_alignment = DEFAULT_AIO_FILE_BLOCK_SIZE;
auto align_up = [=](size_t value) { return (value + min_alignment - 1) / min_alignment * min_alignment; };
size_t buffer_alignment = alignment == 0 ? min_alignment : align_up(alignment);
size_t buffer_size = settings.local_fs_buffer_size;
if (buffer_size % min_alignment)
{
existing_memory = nullptr; /// Cannot reuse existing memory as it has unaligned size.
buffer_size = align_up(buffer_size);
}
if (reinterpret_cast<uintptr_t>(existing_memory) % min_alignment)
{
existing_memory = nullptr; /// Cannot reuse existing memory as it has unaligned offset.
}
/// Attempt to open a file with O_DIRECT
try
{
std::unique_ptr<ReadBufferFromFileBase> res = create(buffer_size, buffer_alignment, flags | O_DIRECT);
ProfileEvents::increment(ProfileEvents::CreatedReadBufferDirectIO);
return res;
}
catch (const ErrnoException &)
{
/// Fallback to cached IO if O_DIRECT is not supported.
ProfileEvents::increment(ProfileEvents::CreatedReadBufferDirectIOFailed);
}
}
#endif
ProfileEvents::increment(ProfileEvents::CreatedReadBufferOrdinary);
size_t buffer_size = settings.local_fs_buffer_size;
/// Check if the buffer can be smaller than default
if (read_hint.has_value() && *read_hint > 0 && *read_hint < buffer_size)
buffer_size = *read_hint;
if (file_size.has_value() && *file_size < buffer_size)
buffer_size = *file_size;
return create(buffer_size, alignment, flags);
}
}
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