nickva opened a new pull request, #5398:
URL: https://github.com/apache/couchdb/pull/5398
We can use fdatasync to save 1 extra write per call, for a total of 2 writes
per commit, since we do two sync, one for data block up to the header, then
another after the header.
As of OTP 25 (our oldest supported version):
* On Linux/BSDs: fdatasync()
* On Window: FlushFileBuffers() i.e. the same as for file:sync/1
* On MacOS: fcntl(fd,F_FULLFSYNC/F_BARRIERFSYNC)
According to https://linux.die.net/man/2/fdatasync
> fdatasync() is similar to fsync(), but does not flush modified metadata
unless that metadata is needed in order to allow a subsequent data retrieval
to be correctly handled. For example, changes to st_atime or
st_mtime (respectively, time of last access and time of last modification;
see
stat(2)) do not require flushing because they are not necessary for a
subsequent data read to be handled correctly. On the other hand, a change to
the file size (st_size, as made by say ftruncate(2)), would require a
metadata
flush.
The key things for us are:
* It updates the size (positions) correctly
* We do not rely or care about atime/mtime for safety or correctness
* Erlang VM does the right thing on all the supported OSes
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
