Re: [HACKERS] fsync method checking

On Thu, Mar 18, 2004 at 03:34:21PM -0500, Bruce Momjian wrote:
> Kurt Roeckx wrote:
> > Here are my results on Linux 2.6.1 using cvs version 1.7.
> >
> > Those times with > 20 seconds, you really hear the disk go crazy.
> >
> > And I have the feeling something must be wrong. Those results
> > are reproducible.
> >
>
> Wow, your O_SYNC times are great. Where can I buy some? :-)
>
> Anyway, we do need to find a way to test this because obviously there is
> huge platform variability.

New results with version 1.8:

Simple write timing:
write 0.150613

Compare fsync times on write() and non-write() descriptor:
(If the times are similar, fsync() can sync data written
on a different descriptor.)
write, fsync, close 9.170472
write, close, fsync 8.851715

Compare one o_sync write to two:
one 16k o_sync write 2.617860
two 8k o_sync writes 2.563437

Compare file sync methods with one 8k write:
(o_dsync unavailable)
open o_sync, write 1.031721
write, fdatasync 25.599010
write, fsync, 26.192824

Compare file sync methods with 2 8k writes:
(The fastest should be used for wal_sync_method)
(o_dsync unavailable)
open o_sync, write 2.268718
write, fdatasync 27.029396
write, fsync, 27.399243