msync is not supposed to have anything to do with whether the changes are committed to the logical state of the file, or whether other processes using mmap or read to access the file see the changes; it's purely an analogue of fsync and should be treated as a no-op except for the purposes of ensuring data integrity in the event of power failure ...

2013年4月6日 · On at least one system, man msync says: The msync() system call writes modified whole pages back to the filesystem and updates the file modification time. Only those pages containing addr and len-1 succeeding locations will be examined.

2017年10月19日 · On Linux msync(MS_ASYNC) is a no-op (see the VERSIONS section of the msync() man page). On other OSes it may do something and of course you can call msync() with other parameters. If you need to know whether syncing completed and you're willing to block until it has, you can use msync(MS_SYNC) (notice the lack the A).

2023年1月13日 · It does the same stuff basicly, while msync ensures that any changes made to the memory-mapped region are written to the storage device. fsync ensures that any changes made to the file or directory are written to the storage device INCLUDING changes made to the file system's in-memory data structures. And that is useful if you want to ensure ...

2020年2月12日 · Linux version: 4.19 Platform: Xilinx Ultrascale+ Zynq In the programmable logic I've created a memory mapped device located at physical address 0xA0001000. I'm using uio_pdrv_genirq as my device

Actually, msync is largely a no-op on Linux or any system with a proper virtual memory and page cache system; read will immediately see anything written to the mmapped pages, even without msync. It's largely an analog of fsync , but with a memory address range rather than a file descriptor as its argument.

2009年3月6日 · When I read the man page for msync, I would not assume that it is actually flushing the disk cache (the cache in the disk unit, as opposed to the system cache in main memory). FlushViewOfFile won't return until the disk stack has completed the writes; like the msync documentation, it says nothing about what happens in the disk cache.

2011年6月9日 · The msync man page states: ENOMEM The indicated memory (or part of it) was not mapped. That's the errno value perror() prints for you. So you're somehow trying to msync() memory that you've not mmap()'ed from a file.

I'm currently using OpenLDAP Symas MDB as a persistent key/value storage and without MDB_MAPASYNC - which results in using msync(MS_ASYNC) (I looked through the source code) - the writes are so slow, that even while processing data a single core is permanently waiting on IO at sometimes < 1MB/s. After analyzing, the problem seems to be many ...

2015年7月21日 · Changes are not dropped if msync() was not called before close()/munmap(). MS_ASYNC is a no-op. MS_SYNC is just like fsync(). In Linux, msync() is just another interface to fsync() and nothing more. See msync(2) manual page and this thread. Reference. See "The Linux Programming Interface", section "49.4.4 Memory Protection and File Access Mode ...