Re: test_fsync label adjustments

A.M. wrote:
>
> On Jan 18, 2011, at 3:55 PM, Bruce Momjian wrote:
>
> > I have modified test_fsync to use test labels that match wal_sync_method
> > values, and and added more tests for open_sync with different sizes.
> > This should make the program easier for novices to understand. Here is
> > a test run for Ubuntu 11.04:
> >
> > $ ./test_fsync
> > 2000 operations per test
> >
> > Compare file sync methods using one 8k write:
> > (in wal_sync_method preference order, except fdatasync
> > is Linux's default)
> > open_datasync (non-direct I/O)* 85.127 ops/sec
> > open_datasync (direct I/O) 87.119 ops/sec
> > fdatasync 81.006 ops/sec
> > fsync 82.621 ops/sec
> > fsync_writethrough n/a
> > open_sync (non-direct I/O)* 84.412 ops/sec
> > open_sync (direct I/O) 91.006 ops/sec
> > * This non-direct I/O mode is not used by Postgres.
>
> I am curious how this is targeted at novices. A naive user might enable
> the "fastest" option which could be exactly wrong. For this to be useful
> to novices, I suspect the tool will need to generate platform-specific
> suggestions, no?

Uh, why isn't the fastest option right for them? It is hardware/kernel
specific when you run it --- how could it be better?

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +