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

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Greg Stark <gsstark(at)mit(dot)edu>
Cc: Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers(at)postgresql(dot)org, pgsql-performance(at)postgresql(dot)org, Michael Clemmons <glassresistor(at)gmail(dot)com>, Hannu Krosing <hannu(at)2ndquadrant(dot)com>, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>
Subject: Re: [HACKERS] Re: Faster CREATE DATABASE by delaying fsync (was 8.4.1 ubuntu karmic slow createdb)
Date: 2010-01-19 15:25:46
Message-ID: 9319.1263914746@sss.pgh.pa.us
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Greg Stark <gsstark(at)mit(dot)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

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