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Re: [HACKERS] Re: Faster CREATE DATABASE by delaying fsync (was 8.4.1 ubuntu karmic slow createdb)

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Greg Stark <gsstark@mit.edu>
Cc: Andres Freund <andres@anarazel.de>, pgsql-hackers@postgresql.org, pgsql-performance@postgresql.org, Michael Clemmons <glassresistor@gmail.com>, Hannu Krosing <hannu@2ndquadrant.com>, Scott Marlowe <scott.marlowe@gmail.com>
Date: 2010-01-19T15:25:46Z
Lists: pgsql-hackers, pgsql-performance 
Greg Stark <gsstark@mit.edu> writes:
> 1) moved the posix_fadvise call to a new fd.c function
> pg_fsync_start(fd,offset,nbytes) which initiates an fsync without
> waiting on it. Currently it's only implemented with
> posix_fadvise(DONT_NEED) but I want to look into using sync_file_range
> in the future -- it looks like this call might be good enough for our
> checkpoints.

That function *seriously* needs documentation, in particular the fact
that it's a no-op on machines without the right kernel call.  The name
you've chosen is very bad for those semantics.  I'd pick something
else myself.  Maybe "pg_start_data_flush" or something like that?

Other than that quibble it seems basically sane.

			regards, tom lane