A.M. wrote: > > On Jan 18, 2011, at 5:16 PM, Bruce Momjian wrote: > > > 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? > > Because the fastest option may not be syncing to disk. For example, > the only option that makes sense on OS X is fsync_writethrough- it > would be helpful if the tool pointed that out (on OS X only, obviously).
Yes, that would be a serious problem. :-( I am not sure how we would address this --- your point is a good one. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
