More numbers, these from a Powerbook G3 laptop running Linux 2.2:
[tgl@g3 tmp]$ uname -a
Linux g3 2.2.18-4hpmac #1 Thu Dec 21 15:16:15 MST 2000 ppc unknown
[tgl@g3 tmp]$ gcc -Wall -O -DINIT_WRITE -DUSE_DSYNC -DBLOCKS=1 tfsync.c
[tgl@g3 tmp]$ time ./a.out
real 0m32.418s
user 0m0.020s
sys 0m14.020s
[tgl@g3 tmp]$ gcc -Wall -O -DINIT_WRITE -DUSE_DSYNC -DBLOCKS=4 tfsync.c
[tgl@g3 tmp]$ time ./a.out
real 0m10.894s
user 0m0.000s
sys 0m4.030s
[tgl@g3 tmp]$ gcc -Wall -O -DINIT_WRITE -DUSE_DSYNC -DBLOCKS=8 tfsync.c
[tgl@g3 tmp]$ time ./a.out
real 0m7.211s
user 0m0.000s
sys 0m2.200s
[tgl@g3 tmp]$ gcc -Wall -O -DINIT_WRITE -DUSE_DSYNC -DBLOCKS=32 tfsync.c
[tgl@g3 tmp]$ time ./a.out
real 0m4.441s
user 0m0.020s
sys 0m0.870s
[tgl@g3 tmp]$ gcc -Wall -O -DINIT_WRITE -DUSE_DSYNC -DBLOCKS=64 tfsync.c
[tgl@g3 tmp]$ time ./a.out
real 0m4.488s
user 0m0.000s
sys 0m0.640s
[tgl@g3 tmp]$ gcc -Wall -O -DINIT_WRITE -DUSE_ODSYNC -DBLOCKS=1 tfsync.c
[tgl@g3 tmp]$ time ./a.out
real 0m3.725s
user 0m0.000s
sys 0m0.310s
[tgl@g3 tmp]$ gcc -Wall -O -DINIT_WRITE -DUSE_ODSYNC -DBLOCKS=4 tfsync.c
[tgl@g3 tmp]$ time ./a.out
real 0m3.785s
user 0m0.000s
sys 0m0.290s
[tgl@g3 tmp]$ gcc -Wall -O -DINIT_WRITE -DUSE_ODSYNC -DBLOCKS=64 tfsync.c
[tgl@g3 tmp]$ time ./a.out
real 0m3.753s
user 0m0.010s
sys 0m0.300s
Starting to look like we should just use ODSYNC where available, and
forget about dumping more per write ...
regards, tom lane
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