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Use async file handle for better parallelism (#1049)

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This commit is contained in:
PraveenSinghRao 2016-04-22 13:27:33 -07:00 committed by Siying Dong
parent c146c9be18
commit b54c347424
1 changed files with 29 additions and 4 deletions
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33
port/win/env_win.cc
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@ -124,6 +124,8 @@ SSIZE_T pwrite(HANDLE hFile, const char* src, size_t numBytes,
}
// See comments for pwrite above
// PLEASE NOTE: hFile is expected to be an async handle
// (i.e. opened with FILE_FLAG_OVERLAPPED)
SSIZE_T pread(HANDLE hFile, char* src, size_t numBytes, uint64_t offset) {
assert(numBytes <= std::numeric_limits<DWORD>::max());
OVERLAPPED overlapped = {0};
@ -132,18 +134,33 @@ SSIZE_T pread(HANDLE hFile, char* src, size_t numBytes, uint64_t offset) {
overlapped.Offset = offsetUnion.LowPart;
overlapped.OffsetHigh = offsetUnion.HighPart;
overlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
if (NULL == overlapped.hEvent) {
return -1;
}
SSIZE_T result = 0;
unsigned long bytesRead = 0;
DWORD lastError = ERROR_SUCCESS;
if (FALSE == ReadFile(hFile, src, static_cast<DWORD>(numBytes), &bytesRead,
&overlapped)) {
return -1;
if ((FALSE == ReadFile(hFile, src, static_cast<DWORD>(numBytes), &bytesRead,
&overlapped)) && ((lastError = GetLastError()) != ERROR_IO_PENDING)) {
result = (lastError == ERROR_HANDLE_EOF) ? 0 : -1;
} else {
result = bytesRead;
if (lastError == ERROR_IO_PENDING) { //otherwise bytesRead already has the result
if (FALSE == GetOverlappedResult(hFile, &overlapped, &bytesRead, TRUE)) {
result = (GetLastError() == ERROR_HANDLE_EOF) ? 0 : -1;
}
else {
result = bytesRead;
}
}
}
CloseHandle(overlapped.hEvent);
return result;
}
@ -684,6 +701,8 @@ class WinSequentialFile : public SequentialFile {
// pread() based random-access
class WinRandomAccessFile : public RandomAccessFile {
const std::string filename_;
// PLEASE NOTE: hFile is expected to be an async handle
// (i.e. opened with FILE_FLAG_OVERLAPPED)
HANDLE hFile_;
const bool use_os_buffer_;
bool read_ahead_;
@ -1225,6 +1244,12 @@ class WinEnv : public Env {
fileFlags |= FILE_FLAG_RANDOM_ACCESS;
}
if (!options.use_mmap_reads) {
// Open in async mode which makes Windows allow more parallelism even
// if we need to do sync I/O on top of it.
fileFlags |= FILE_FLAG_OVERLAPPED;
}
/// Shared access is necessary for corruption test to pass
// almost all tests would work with a possible exception of fault_injection
HANDLE hFile = 0;