On 13/10/2010 12:38 AM, Jesper Krogh wrote:
If some clever postgres hacker could teach postgres to allocate blocks using posix_fallocate in quite large batches, say .. something like: fallocate(min(current_relation_size *0.1,1073741824))
There doesn't seem to be any use of posix_fallocate in the sources, at least according to git grep. The patch that introduced posix_fadvise use apparently had posix_fallocate in it, but that use appears to have been removed down the track.
It's worth noting that posix_fallocate sucks if your file system doesn't intelligent support for it. IIRC it's horrible on ext3, where it can take a while to return while it allocates (and IIRC zeroes!) all those blocks. This may be part of why it's not used. In past testing with posix_fallocate for other tools I've also found rather mixed performance results - it can slow things down rather than speed them up, depending on the file system in use and all sorts of other factors.
If Pg was to use posix_fallocate, it'd probably need control over it on a per-tablespace basis.
-- Craig Ringer Tech-related writing at http://soapyfrogs.blogspot.com/ -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
