> Running the attached test program shows on BSD/OS 4.3:
> 
> 	write                  0.000360
> 	write & fsync          0.001391

I think the "write & fsync" pays for the previous "write" test (same filename).

> 	write, close & fsync   0.001308
> 	open o_fsync, write    0.000924

I have tried to modify the program to more closely resemble WAL 
writes (all writes to WAL are 8k), the file is usually already open, 
and test larger (16k) transactions.

zeu@a82101002:~> test_sync1
write                      0.000625
write & fsync              0.016748
write & fdatasync          0.006650
write, close & fsync       0.017084
write, close & fdatasync   0.006890
open o_dsync, write        0.015997
open o_dsync, one write    0.007128

For the last line xlog.c would need to be modified, but the measurements
seem to imply that it is only worth it on platforms that have O_DSYNC
but not fdatasync.  

Andreas
Fri, 12 Dec 2003 13:22:00 +0100
"Zeugswetter Andreas SB SD" <ZeugswetterA@spardat.at>
Re: [HACKERS] fsync method checking

I have updated my program with your suggested changes and put in
src/tools/fsync.  Please see how you like it.

---------------------------------------------------------------------------

Zeugswetter Andreas SB SD wrote:
> 
> > Running the attached test program shows on BSD/OS 4.3:
> > 
> > 	write                  0.000360
> > 	write & fsync          0.001391
> 
> I think the "write & fsync" pays for the previous "write" test (same filename).
> 
> > 	write, close & fsync   0.001308
> > 	open o_fsync, write    0.000924
> 
> I have tried to modify the program to more closely resemble WAL 
> writes (all writes to WAL are 8k), the file is usually already open, 
> and test larger (16k) transactions.
> 
> zeu@a82101002:~> test_sync1
> write                      0.000625
> write & fsync              0.016748
> write & fdatasync          0.006650
> write, close & fsync       0.017084
> write, close & fdatasync   0.006890
> open o_dsync, write        0.015997
> open o_dsync, one write    0.007128
> 
> For the last line xlog.c would need to be modified, but the measurements
> seem to imply that it is only worth it on platforms that have O_DSYNC
> but not fdatasync.  
> 
> Andreas

Content-Description: test_sync1.c

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Thu, 18 Mar 2004 12:34:36 -0500 (EST)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: [HACKERS] fsync method checking