script(s) for tracking execution paths

[William Cohen]

Tom Zanussi wrote:
> William Cohen writes:
>  > Tom Zanussi wrote:
>  > > Hi,
>  > > 
>  > > I've been having some fun playing around with maps keyed on stack
>  > > traces (very cool to be able to do this) and have checked into
>  > > systemtap.samples a systemtap script (kmalloc-stacks.stp) and a perl
>  > > script (kmalloc-top) that in combination continuously track the
>  > > different execution paths to kmalloc().  It keeps counts of the
>  > > different execution paths in a systemtap hash, and periodically dumps
>  > > the hash contents (and clears the hash table) to the perl script,
>  > > which rehashes them in user space.  At the end of the run (Ctrl-C), it
>  > > sorts the accumulated hash table and filters out any stacks that
>  > > contain any of the user-supplied regexps (-e option), which helps cut
>  > > down on noise e.g.
>  > > 
>  > > # ./kmalloc-top -e sys_select,alloc_skb
>  > > 
>  > > Here's an example of the output (gathered over a kernel compile):
>  > 
>  > Hi Tom, I have been playing around with the kmalloc example you checked 
>  > in. When running it, I have seen a couple panics like the one in the 
>  > photo at:
>  > 
>  > http://people.redhat.com/wcohen/100_0405.jpg
>  > 
>  > This is on a pentium III machine running the rawhide with the current 
>  > kernel:
>  > 
>  > Linux trek.devel.redhat.com 2.6.13-1.1555_FC5smp #1 SMP Wed Sep 14 
>  > 15:59:49 EDT 2005 i686 i686 i386 GNU/Linux
>  > 
>  > 
> 
> Hmm, I haven't seen anything like that on my machine, a Pentium 4
> running 2.6.12-1.1447_FC4.
> 
> Is there anything in particular you do to make it happen?  The
> sytemtap script itself is pretty simple and doesn't do anything out of
> the ordinary as far as I can tell.  I see _stp_map_del() in the trace
> - is that always the case?
> 
> Tom

I started the kmalloc-top in one login and did a compile of systemtap in 
the other. I was using the stap from the RPM build earlier this week, 
0.4.1. Looking at the other picture I took I also see _stp_map_del() 
there too.

-Will