On Tuesday, March 13, 2012 04:49:40 AM Jeff Davis wrote: > On Sun, 2012-02-05 at 17:56 -0500, Noah Misch wrote: > > I meant primarily to illustrate the need to be comprehensive, not comment > > on which executable should fsync a particular file. Bootstrap-mode > > backends do not sync anything during an initdb run on my system. With > > your patch, we'll fsync a small handful of files and leave nearly > > everything else vulnerable. > > Thank you for pointing that out. With that in mind, I have a new version > of the patch which just recursively fsync's the whole directory > (attached). > > I also introduced a new option --nosync (-N) to disable this behavior. > > The bad news is that it introduces a lot more time to initdb -- it goes > from about 1s to about 10s on my machine. I tried fsync'ing the whole > directory twice just to make sure that the second was a no-op, and > indeed it didn't make much difference (still about 10s). I suggest you try making it two loops:
for recursively everything in dir: posix_fadvise(fd, POSIX_FADV_DONTNEED); for recursively everything in dir: fsync(fd); In my experience that gives way much better performance due to the fact that it does not force its own metadata/journal commit/transaction for every file but can be batched. copydir() does the same since some releases... Obviously its not that nice to use _DONTNEED but I havent found something that works equally well. You could try sync_file_range(fd, 0, 0, SYNC_FILE_RANGE_WRITE) in the first loop but my experience with that hasn't been that good. Andres -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
