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Re: pfaults.stp


On 09/04/2013 05:14 PM, Paddie O'Brien wrote:
> Hi,
> 
> I'm running a simple program and attempting to use examples/memory/pfaults.stp
> to see the page faults it generates. The program runs but pfaults.stp
> stays quiet
> every time (even the first). I know I'm missing something stupid but...
> 
> Shouldn't I see something?!
> 
> Thanks,
> Paddie
> 

Hi Paddie,

On Fedora 19 running on an x86_64 machine I just ran the example and I got the expected output like:

$  stap pfaults.stp
...
18974551:2368:0x7f6e429bf000:w:minor:11
18974610:2368:0x7f6e429c0000:w:minor:1
18974671:2368:0x7f6e429c1000:w:minor:1
18974743:2368:0x7f6e429c2000:w:minor:11
18974801:2368:0x7f6e429c3000:w:minor:1
18974858:2368:0x7f6e429c4000:w:minor:0
18974920:2368:0x7f6e429c5000:w:minor:1

You might also do "stap -v pfaults.stp" to see if is just taking a while to get the instrumentation started. On a machine that everything has been running a while you might not get much output.  Did you try to start a new program to trigger some page faults?  You can check that you are getting some page faults doing something like:

$ /usr/bin/time calc
/usr/bin/time: cannot run calc: No such file or directory
0.00user 0.00system 0:00.00elapsed 0%CPU (0avgtext+0avgdata 248maxresident)k
0inputs+0outputs (0major+49minor)pagefaults 0swaps


Could you provide a bit more information about the environment you are running things in as listed on https://sourceware.org/systemtap/wiki/HowToReportBugs?

-Will


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