Re: How to profile kernel (for both 2.4 and 2.6)

[William C. <wc...@nc...>]

=C3=F7 =C0=EE wrote:
> Hi,
> =20
> I have a stress test on two systems, one x86, one ia64. and sys% cpu is=
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> over 30%, I just what to kown what happens in it.
> =20
> I've oprofile 0.8.1 on rhel4 x86 rc, and 0.5.4 on rhel3 U4 ia64. =20
> They're installed with OS, I did not re-installed by myself.
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> After read from FAQ, I should be able to profile kernel and see samples=
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> on kernel symbols with :
> #opcontrol --init
> #opcontrol --reset
> #opcontrol --setup --vmlinux=3D/boot/vmlinux
> #opcontrol --start
> #opreport -l (or op_time -l from 0.5.4)
> =20
> But the result is, I did not see anything around kernel, only some=20
> lib.so files.
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> For my two servers, they don't have vmlinux, so I recompiled source and=
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> managed created vmlinux file, so I just cp this file to /boot/vmlinux.
> =20
> I'm curious to know, this kernel file might be different to the vmlinuz=
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> loaded at bootup. How can I profile the real kernel within my running=20
> system, am I misunderstanding some operations or sth?

As a part of the build process at Red Hat debuginfo rpms are built. The
debuginfo rpms contain the -g information stripped out of the
executable. For the kernel a similar process is performed and the
vmlinux files and debug information from modules are included in the
debuginfo rpm for the kernel.

However, for the time being the debuginfo rpms are not made available to
the general public like the rpms Red Hat supplies for RHEL. This should
be changing in the future. The debug information is really useful for
mapping profiling data back to the source code.

The debuginfo rpms are available for Fedora core.

For regular executables there is a checksum verfication to make sure
that the debug information matches the executable. For the kernel there
is no verification, so it is possible to point oprofile at one vmlinux
when using a different kernel. You need to make sure that they match.

-Will