FileReader::readDirect implementation with O_DIRECT/F_NOCACHE: https://github.com/airdcpp/airdcpp- windows/commit/eb1e075d5a69862c4f2255f9ea2f204bb70921ba
However, I don't think that the main point of the low-level FileReader::readDirect implementation for Windows is skipping of the OS buffers (couldn't you use the regular File class with FILE_FLAG_NO_BUFFERING instead?) but the use of OVERLAPPED (async I/O). The closest equivalent for that on Linux would probably be AIO (https://man7.org/linux/man-pages/man7/aio.7.html). So possibly the FileReader methods should rather be called readAsync (overlapped/AIO) and readUnbuffered (FILE_FLAG_NO_BUFFERING/O_DIRECT/F_NOCACHE). Is buffered reading even needed there? When would that work if the unbuffered read fails? -- You received this bug notification because you are a member of Dcplusplus-team, which is subscribed to DC++. https://bugs.launchpad.net/bugs/1909861 Title: FileReader is not thread safe on Linux Status in DC++: New Bug description: FileReader::readMapped currently modifies the global SIGBUS handler in order to catch read errors: https://sourceforge.net/p/dcplusplus/code/ci/default/tree/dcpp/FileReader.cpp#l289 Since the function can be called concurrently from different threads (currently hashing/queue recheck/sfv check in DC++) and each of them sets and resets the SIGBUS handler, there's a high risk that the application will crash in case of read errors as they aren't being handler properly. More information about the caveats: https://www.sublimetext.com/blog/articles/use-mmap-with-care These issues are much more likely to happen with AirDC++ as it uses multiple threads for hashing. Read errors caused rather nasty crashes with corrupted stack traces for one user, but luckily he was able to catch the SIGBUS signal with gdb. I didn't even spend time in trying to figure out how to make the mapped reads work properly, as based on my testing the basic FileReader::readCached function is noticeably faster: readMapped: 671 files (21.70 GiB) in 9 directories have been hashed in 4 minutes 21 seconds (84.87 MiB/s) readCached: 671 files (21.70 GiB) in 9 directories have been hashed in 3 minutes 58 seconds (93.08 MiB/s) FileReader::readMapped is now disabled in AirDC++, as I can't see any benefits from using it. The included setjmp.h header is even causing issues when using clang for compiling on Linux: https://bugs.gentoo.org/731676 To manage notifications about this bug go to: https://bugs.launchpad.net/dcplusplus/+bug/1909861/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~linuxdcpp-team Post to : linuxdcpp-team@lists.launchpad.net Unsubscribe : https://launchpad.net/~linuxdcpp-team More help : https://help.launchpad.net/ListHelp
