stubbs@ncr-sd.SanDiego.NCR.COM (Jan Stubbs) (05/23/87)
IOCALL, A UNIX SYSTEM PERFORMANCE BENCHMARK
Results as of 5/20/87.
This version of the benchmark does 10,000 iterations instead of
1000. Unix machines are getting so fast that 1000 was too quick
to measure accurately on some CPU's.
Send your results to me directly. The benchmark is a "C" program
which measures Unix kernel performance.
To run it put the source below in iocall.c, then:
cc iocall.c -o iocall
time iocall
Send all 3 times (user, system, real), but I am reporting the system
time only, the user time for this benchmark is usually insignificant.
"The opinions expressed herein are those of the author. Your mileage may vary".
Benchmark should be run on an otherwise idle machine. If you can please
run them so, it does improve the timings.
COMMENTARY:
What does this benchmark measure? It attempts to simulate a typical mix
of reading, writing and seeking on a Unix kernel, and uses the time
command to let the kernel measure its cpu time.
It exercises the system call interface in a way less trivial than the
getpid benchmark. It does not measure and is independent of, your IO hardware,
and drivers. It does seem to show differences in Unix kernel efficiency on
the same hardware. It will exercise heavily your caches, and perhaps
your block move bandwidth.
I have had some criticism of this benchmark to whit:
It unfairly penalizes machines which do not have CPU data cacheing on the
Unix buffer pool.
My Response:
It does penalize such machines, because it heavily emphazises the function
of copying data from the buffer pool and back again. No benchmark is
perfect, but this one shows what a very IO intensive workload might
be like on your machine.
Many synthetic benchmarks are criticized for giving unrealistic
results when run through optimizers that may throw out stuff that
does nothing useful. This is NOT a problem with IOCALL. If your
compiler finds something in the UNIX kernel that does nothing useful
and throws it out, MORE POWER TO IT!
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/*This benchmark tests speed of Unix system call interface
and speed of cpu doing common Unix io system calls. */
char buf[512];
int fd,count,i,j;
main()
{
fd = creat("/tmp/testfile",0777);
close(fd);
fd = open("/tmp/testfile",2);
unlink("/tmp/testfile");
for (i=0;i<=10000;i++) {
lseek(fd,0L,0); /* add this line! */
count = write(fd,buf,500);
lseek(fd,0L,0); /* second argument must be long */
for (j=0;j<=3;j++)
count = read(fd,buf,100);
}
}
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"There are lies, damn lies, and benchmarks."
Jan Stubbs ....sdcsvax!ncr-sd!stubbs
619 485-3052
NCR Corporation Advanced Development
16550 W. Bernardo Drive MS4010
San Diego, CA. 92127