JD,
In order to test real interactivity (AFAIK) with iozone you have to
launch multiple iozone instances. You also need to do them from separate
directories, otherwise it all starts writing the same file. The work I
did here:
Actually, current IOZone allows you to specify multiple files. For
example, the command line I was using:
iozone -R -i 0 -i 1 -i 2 -i 3 -i 4 -i 5 -i 8 -l 6 -u 6 -r 8k -s 4G -F f1
f2 f3 f4 f5 f6
And it does indeed launch 6 processes under that configuration.
However, I found that for pretty much all of the write tests except for
the first the processes blocked each other:
F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME CMD
0 S 26 6061 5825 0 80 0 - 11714 wait pts/3 00:00:00 iozone
1 D 26 6238 6061 0 78 0 - 11714 sync_p pts/3 00:00:03 iozone
1 D 26 6239 6061 0 78 0 - 11714 sync_p pts/3 00:00:03 iozone
1 D 26 6240 6061 0 78 0 - 11714 sync_p pts/3 00:00:03 iozone
1 D 26 6241 6061 0 78 0 - 11714 sync_p pts/3 00:00:03 iozone
1 D 26 6242 6061 0 78 0 - 11714 stext pts/3 00:00:03 iozone
1 R 26 6243 6061 0 78 0 - 11714 - pts/3 00:00:03 iozone
Don Capps says that the IOZone code is perfect, and that pattern
indicates a problem with my system, which is possible. Can someone else
try concurrent IOZone on their system and see if they get the same
pattern? I just don't have that many multi-core machines to test on.
Also, WTF is the difference between "Children See" and "Parent Sees"?
IOZone doesn't document this anywhere.
--
Josh Berkus
PostgreSQL Experts Inc.
www.pgexperts.com
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