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2013-01-09Add file:allocate/3 operationFilipe David Manana
This operation allows pre-allocation of space for files. It succeeds only on systems that support such operation. The POSIX standard defines the optional system call posix_fallocate() to implement this feature. However, some systems implement more specific functions to accomplish the same operation. On Linux, if the more specific function fallocate() is implemented, it is used instead of posix_fallocate(), falling back to posix_fallocate() if the fallocate() call failed (it's only supported for the ext4, ocfs2, xfs and btrfs file systems at the moment). On Mac OS X it uses the specific fcntl() operation F_PREALLOCATE, falling back to posix_fallocate() if it's available (at the moment Mac OS X doesn't provide posix_fallocate()). On any other UNIX system, it uses posix_fallocate() if it's available. Any other system not providing this system call or any function to pre-allocate space for files, this operation always fails with the ENOTSUP POSIX error.
2010-05-24Merge branch 'fm/file-operations' into devErlang/OTP
* fm/file-operations: Update preloaded modules Add file:advise/4 - a wrapper to the POSIX syscall posix_fadvise Add file:datasync/1 for syncing file contents only sys.h: Correct the get_int64() macro OTP-8637 fm/file-operations The functions file:advise/4 and file:datasync/1 have been added. (Thanks to Filipe David Manana.)
2010-05-20Add file:advise/4 - a wrapper to the POSIX syscall posix_fadviseFilipe David Manana
Useful for informing the Operating System about the access pattern for a file's data, so that it can adapt the caching strategy to maximize disk IO performance.
2010-05-20Add file:datasync/1 for syncing file contents onlyFilipe David Manana
file:datasync/1 invokes the POSIX system call "int fdatasync(int fd)". This system call is similar to "fsync" but, unlike fsync, it does not update the metadata associated with the file (like the access time for example). It's used by many DBMSs (MySQL and SQLite of example) to increase disk IO performance, as it avoids disk seeks and disk write operations compared to fsync. More details on it at: http://linux.die.net/man/2/fdatasync An example, from the MySQL source: http://bazaar.launchpad.net/~mysql/mysql-server/mysql-5.1-telco-6.1/annotate/head%3A/mysys/my_sync.c#L61 This new function just calls fsync on systems not implementing fdatasync.
2009-11-20The R13B03 release.OTP_R13B03Erlang/OTP