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Re: Instrumenting context switches
- From: Perry Cheng <perryche at us dot ibm dot com>
- To: dave_sperry at ieee dot nospam dot dot dot org, systemtap at sourceware dot org
- Date: Thu, 30 Nov 2006 18:08:36 -0500
- Subject: Re: Instrumenting context switches
Hi Dave,
I was using version 0.4 and have upgraded to version 0.5.11 like you
(mine's from today though and not 11/20).
However, the new stap can't find the probe points. I suspect that it is
not locating the kernel symbols file.
Do you know how to get the info out of the old /usr/bin/stap and give it
to the new /usr/local/bin/stap?
Perry
systemtap-owner@sourceware.org wrote on 11/30/2006 05:01:25 PM:
> Perry,
> I had no problem running your systemtap scripts on my AMD-686 SMP box
> running the same kernel as you list below.
>
> I did a stap perry.stp -vvvv -g &>perryFoo.txt and it worked just fine.
> You can see the log at:
>
> http://toomanyprojects.org:2000/outbound/perry/perryFoo.txt
>
>
> The version of systemtap I used is:
>
> SystemTap translator/driver (version 0.5.11 built 2006-11-20)
> (Using Red Hat elfutils 0.124 libraries.)
> Copyright (C) 2005-2006 Red Hat, Inc. and others
> This is free software; see the source for copying conditions.
>
>
> Dave
>
> > Perry Cheng
> > <perryche@us.ibm.
> > com> To
> > Sent by: Martin Hunt <hunt@redhat.com>,
> > systemtap-owner@s systemtap@sourceware.org
> > ourceware.org cc
> >
> > Subject
> > 11/30/2006 03:29 Re: Instrumenting context
switches
> > PM
> >
> > The following even simpler program also dies and rules out
gettimeofday or
> > accessing a global variable as possible causes. The crash happens on
both
> > an intel-686 and AMD-686 both running a modified version of 2.6.16. I
> > don't know the details of the modifications but they are generally
used to
> > support real-time features and include the hrt and rt-prio patches.
The
> > src is at ftp://linuxpatch.ncsa.uiuc.edu/rt-linux/rhel4u2/R1-iFix1.
> >
> > If I replace __switch_to with context_switch or finish_task_switch,
the
> > failure still occurs. However, if I switch to set_task_comm, then
things
> > seem ok.
> >
> > probe kernel.function("__switch_to")
> > {
> > foobar()
> > }
> >
> > function foobar()
> > %{
> > _stp_printf("foobar\n");
> > %}
> >
> > Perry
> >
> >
> > systemtap-owner@sourceware.org wrote on 11/30/2006 10:31:10 AM:
> >
> > > On Wed, 2006-11-29 at 18:25 -0500, Perry Cheng wrote:
> > >
> > > > probe kernel.function("__switch_to")
> > > > {
> > > > doSwitchTo(gettimeofday_us(), $prev_p, $next_p);
> > > > }
> > > >
> > > > function doSwitchTo(timeus:long, prev:long, next:long)
> > > > %{
> > > > _stp_printf("SWITCHCOUNT = %ld\n", switchCount);
> > > > <------------------------------ BAD LINE
> > > > switchCount++;
> > > > }%
> > >
> > > Obviously the code fragment above is not exactly what you are using
to
> > > reproduce the bug. (You can't use keywords as parameter names,
> > > uninitialized switchCount, "}%", etc). I tried the following and
did
> > > not see any problems. Can you give more details (arch, OS, etc) on
how
> > > to reproduce?
> > >
> > > %{
> > > long switchCount = 1000000;
> > > %}
> > >
> > > function doSwitchTo (t:long, p:long, n:long) %{
> > > _stp_printf("SWITCHCOUNT = %ld\n", switchCount);
> > > switchCount++;
> > > %}
> > >
> > > probe kernel.function("__switch_to")
> > > {
> > > doSwitchTo(gettimeofday_us(), $prev_p, $next_p);
> > > }
> > >
> > >
> > >
> >
> >
>