SystemTap on Ubuntu 7.04 i386

SystemTap on Ubuntu 7.04 i386

[Mike Mason]

I discovered that Ubuntu has a kernel-debug package that provides an unstripped vmlinux only (no modules).  Perhaps this is general knowledge, but it was news to me.  The installed vmlinux is named /boot/vmlinux-dbg-<version>, so I created a link to it named vmlinux-<version> so systemtap can find it.  Then I built and installed the latest systemtap in CVS (as of yesterday) and ran "make installcheck".  I was surprised to see very few failures (see below).  I haven't evaluated the failures yet. Obviously anything related to modules can be explained.  I also tried a few of the example scripts and they worked as well, with the exception of socktop because the sockets tapset was broken at the time the FC7 snapshot was taken.  All this with just a 57MB vmlinux debuginfo file.

I'm wondering if we could get the distros to install the vmlinux-only debuginfo by default.  I'm guessing this would allow 95% of systemtap to work out-of-box.

BTW, Ubuntu 7.04 does bundle a version of systemtap, but it seems rather old.

Mike

Test Run By root on Mon Jun  4 15:14:11 2007
Native configuration is i686-pc-linux-gnu

FAIL: systemtap.base/kmodule.stp compilation
FAIL: buildok/eighteen.stp
FAIL: buildok/four.stp
FAIL: buildok/scsi.stp
FAIL: buildok/twentyfive.stp
FAIL: semok/twelve.stp
FAIL: semok/twenty.stp
FAIL: systemtap.samples/lket(semantic error)
FAIL: transport fill staging buffer - relayfs (0)
FAIL: systemtap.stress/current.stp compilation

		=== systemtap Summary ===

# of expected passes		309
# of unexpected failures	10
# of expected failures		130
# of unknown successes		2
# of known failures		5
# of untested testcases		30
# of unsupported tests		1

Re: SystemTap on Ubuntu 7.04 i386

[Mike Mason]

BTW, does anyone object to changing stap to search for vmlinux-dbg-<version>, too?

Mike

Mike Mason wrote:
> I discovered that Ubuntu has a kernel-debug package that provides an 
> unstripped vmlinux only (no modules).  Perhaps this is general 
> knowledge, but it was news to me.  The installed vmlinux is named 
> /boot/vmlinux-dbg-<version>, so I created a link to it named 
> vmlinux-<version> so systemtap can find it.  Then I built and installed 
> the latest systemtap in CVS (as of yesterday) and ran "make 
> installcheck".  I was surprised to see very few failures (see below).  I 
> haven't evaluated the failures yet. Obviously anything related to 
> modules can be explained.  I also tried a few of the example scripts and 
> they worked as well, with the exception of socktop because the sockets 
> tapset was broken at the time the FC7 snapshot was taken.  All this with 
> just a 57MB vmlinux debuginfo file.
> 
> I'm wondering if we could get the distros to install the vmlinux-only 
> debuginfo by default.  I'm guessing this would allow 95% of systemtap to 
> work out-of-box.
> 
> BTW, Ubuntu 7.04 does bundle a version of systemtap, but it seems rather 
> old.
> 
> Mike
> 
> Test Run By root on Mon Jun  4 15:14:11 2007
> Native configuration is i686-pc-linux-gnu
> 
> FAIL: systemtap.base/kmodule.stp compilation
> FAIL: buildok/eighteen.stp
> FAIL: buildok/four.stp
> FAIL: buildok/scsi.stp
> FAIL: buildok/twentyfive.stp
> FAIL: semok/twelve.stp
> FAIL: semok/twenty.stp
> FAIL: systemtap.samples/lket(semantic error)
> FAIL: transport fill staging buffer - relayfs (0)
> FAIL: systemtap.stress/current.stp compilation
> 
>         === systemtap Summary ===
> 
> # of expected passes        309
> # of unexpected failures    10
> # of expected failures        130
> # of unknown successes        2
> # of known failures        5
> # of untested testcases        30
> # of unsupported tests        1
> 
> 
> 

Re: SystemTap on Ubuntu 7.04 i386

[Peter Bach]

Mike Mason wrote:
> I'm wondering if we could get the distros to install the vmlinux-only 
> debuginfo by default.  I'm guessing this would allow 95% of systemtap 
> to work out-of-box.
This is a great idea, to have the debuginfo available. The situation I 
find myself in is to load the distro (usually RedHat or SuSE), and use 
online repositories to keep up to date. The problem is that if a new 
kernel gets installed, I have to recompile with debuginfo just to get 
the usefulness of SystemTap. I always take the defaults for a kernel 
build, I want to use a computer for useful stuff; I would hate to 
calculate how much time I've wasted compiling kernels just to get 
debuginfo for SystemTap. Is there a better way?

I don't know if this is a function of having the distros compile a 
version with debuginfo, or just making it available in the online 
repositories, but this would seem to be a big hurdle that impedes that 
uptake of SystemTap for all but die hard users.

The real value is that SystemTap is not only useful for solving problems 
in during the development cycle, but illuminates how Linux works under 
the covers, in the most dynamic way, when it is actually running. This 
is much more useful that perusing the code. The target audience for this 
is only every CS student on the planet.

Re: SystemTap on Ubuntu 7.04 i386

[Frank Ch. Eigler]

Peter Bach wrote:

> [...]
> > I'm wondering if we could get the distros to install the
> > vmlinux-only debuginfo by default.  I'm guessing this would allow
> > 95% of systemtap to work out-of-box.

Maybe.  Of the examples, tapsets, and test cases in the source tree,
only a few dozen refer to modules.  Some of them are important: NFS,
SCSI.

> This is a great idea, to have the debuginfo available. The situation
> Innn find myself in is to load the distro (usually RedHat or SuSE),
> and use online repositories to keep up to date. The problem is that
> if a new kernel gets installed, I have to recompile with debuginfo
> just to get the usefulness of SystemTap.

Red Hat (RHEL and Fedora) each publish kernel-debuginfo RPMs for
downloading.  yum can get 'em for you.  Some distributions toss it
away during the build (Debian, Ubuntu), so those need policy changes.

> I don't know if this is a function of having the distros compile a
> version with debuginfo, or just making it available in the online
> repositories, but this would seem to be a big hurdle [...]

We have mentioned the possibility of creating a network server for
debugging information processing.  The idea has not yet been fleshed
out though.


> The real value is that SystemTap is not only useful for solving
> problems in during the development cycle, but illuminates how Linux
> works under the covers, in the most dynamic way, when it is actually
> running. This is much more useful that perusing the code. The target
> audience for this is only every CS student on the planet.

Yeah - mind if I quote you on that? ;-)


- FChE

Re: SystemTap on Ubuntu 7.04 i386

[darrell pfeifer]

On 07 Jun 2007 10:51:17 -0400, Frank Ch. Eigler <fche@redhat.com> wrote:
>
> Peter Bach wrote:
>
> > [...]

[...]

>
> > The real value is that SystemTap is not only useful for solving
> > problems in during the development cycle, but illuminates how Linux
> > works under the covers, in the most dynamic way, when it is actually
> > running. This is much more useful that perusing the code. The target
> > audience for this is only every CS student on the planet.
>
> Yeah - mind if I quote you on that? ;-)
>
>
> - FChE
>

I teach a commercial Linux system internals course. Last year I added
a lab to the course that introduced the students to SystemTap.

At one point we spend several hours learning how to write a loadable
module in order to trace some system data structures. Afterwards, I
show them how to achieve the same result in a few lines of SystemTap
code.

thanks to all the SystemTap people for an invaluable tool.

darrell

Re: SystemTap on Ubuntu 7.04 i386

[Vara Prasad]

darrell pfeifer wrote:

> On 07 Jun 2007 10:51:17 -0400, Frank Ch. Eigler <fche@redhat.com> wrote:
>
>>
>> Peter Bach wrote:
>>
>> > [...]
>
>
> [...]
>
>>
>> > The real value is that SystemTap is not only useful for solving
>> > problems in during the development cycle, but illuminates how Linux
>> > works under the covers, in the most dynamic way, when it is actually
>> > running. This is much more useful that perusing the code. The target
>> > audience for this is only every CS student on the planet.
>>
>> Yeah - mind if I quote you on that? ;-)
>>
>>
>> - FChE
>>
>
> I teach a commercial Linux system internals course. Last year I added
> a lab to the course that introduced the students to SystemTap.
>
> At one point we spend several hours learning how to write a loadable
> module in order to trace some system data structures. Afterwards, I
> show them how to achieve the same result in a few lines of SystemTap
> code.
>
> thanks to all the SystemTap people for an invaluable tool.
>
> darrell

Hi Darrell,

Thanks for such kind words, feedback like this motivates us to make this 
tool better everyday.

I would also appreciate if you can share any experiences on using the 
tool  what works and what doesn't work. Please also share with us any 
interesting scripts either you or your students have written or you want 
us to write.

You can  take a look at Scripts and Tools webpage on the wiki at the 
following link
http://sourceware.org/systemtap/wiki/ScriptsTools

bye,
Vara Prasad