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@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

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