slower on linux

Sinner6 · 07-22-2004, 03:01 PM

I need help. As those familiar with my whining will know I am porting a IA64 program to linux from windows. Everything seems to be going well. EXCEPT performace for one of our libraries(written in almost straight C++).
For test A linux under performs by 15% in test B linux underperforms by 40%!!!

The only difference is that on linux I am using setitimer, signal for SIGALRM, and gettimeofday.
On window I am using CreateTimerQueueTimer, QueryPerformanceCounter.

And yes I am using intels compiler on linux.

Hano · 07-22-2004, 03:58 PM

without more info or the code of the most time consuming parts (have you profiled yet?) is near to impossible to guess what to say to you that may be helpful

Sinner6 · 07-23-2004, 07:10 AM

I can't profile for some reason. I compile gcc foo.cpp -lpthread. and when I run a.out I get a SIGILL for some reason. I am using gcc 3.2.2 on an ia64.

itsme86 · 07-23-2004, 08:24 AM

I think by profiling he means to compile with the -pg option and then to use the gprof command.

Sinner6 · 07-23-2004, 08:41 AM

Yes I compile with -pg and the I get the SIGILL

gcc foo.cpp -pg -lpthread

foo.cpp

const long SIZE = 100000;
int main()
{
long arr[SIZE];
for( int i = 0; i < SIZE; i++ )
arr[i] = (i + 4) * (i - 2) + SIZE - i;

return 0;
}

jim mcnamara · 07-23-2004, 08:53 AM

Do you get SIGKILL when running your compiled code? Not during the compile.

If you run ./a.out you create a mon.out file.
Then
gprof ./a.out
produces the profile information for you.

Sinner6 · 07-23-2004, 09:23 AM

Yea I the SIGILL when I run a.out. It dies before it ever produces gmon.out
The compile looks fine, no warnings, no errors. but the I run a.out and bam SIGILL, Invalid Instruction

jim mcnamara · 07-23-2004, 11:38 AM

Okay. Something is not right. Do you have a thread sending SIGKILL?
Ordinarily applicaions don't send suicide signals unless programmed to do so.

Edit:
I just saw the 'invalid instruction'. You have a library module problem it sounds like. If you know how, try a fully static link. Then run it. Why? We want to make sure the problem is in the shared libraries only, otherwise you found a bug. If nothing else you get to see how much disk space you save by linking shared

itsme86 · 07-23-2004, 12:21 PM

Why do you name the file with a .cpp extension? It looks like it's just C code so should have a .c extension. If you're compiling C++ code use the g++ command. Also, I don't see any thread stuff in there so why are you linking in the pthread library?

Try just: gcc -Wall -pg foo.c -o foo

In fact, profiling won't even give you anything useful because you're not doing any function calls. It will just say it's spending all its time in main().

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Sinner6 · 08-06-2004, 08:44 AM

I upgraded from SuSe 8 to SuSe 9 and that seemed to fix it. Maybe it was a version of a library or gcc but it seems to work now.