Originally posted by: cheungct

Is there any paper talking about the performance enhancement / tuning using xlc v9 on POWER6? We are facing performance degrade using xlc9 compared with xlc8. We have tried to recompile the source code, (with or without -qarh=pwr6 and -qtune=pwr6)and also on/off the SMT, same result we've got.

Moreover, the worst thing if it happened on AIXv5.2 AIXv5.3 and AIXv6.1. Performance drop around 5-10%. Is it the fact using xlc9? please advise. Thanks!

Here's the testing script

===============================================
#include <stdio.h>
#include <stdlib.h>

int
main (int argc, char **argv)
{
long i=0,j=0;

j=atol(argv[1]);

fprintf(stdout, "\nj = %ld\n\n", j);

while (i < j)
{
i++;
}

fprintf(stdout, "\ni = %ld\n\n", i);

}
========================================================

Thomas
#AIX-Forum

Originally posted by: nagger

I think XLC v10 is out now.

How long does this test run for?
I hope a minute at least or you may be spotting some difference in the library handling at start up.

You are, or course, compiling with optimisation - right?
Like -O3

I don't understand your comment on AIX 5.2, 5.3 and 6.1
No one should use AIX 5.2 on POWER6 - it does NOT support SMT at all.

ta N
#AIX-Forum