[Celinux-dev] KFI patch for 2.6.11 kernel ?

[Tim Bird]

Puneet Goel wrote:
> Hello Tim,
> 
> Thanks for the reply. I have been trying this profiling for quite some time
> without any sucess. tried with oprofile also but in vein.
> 
> I have some questions regarding KFI.
> 
> 1. I want to use KFI for mips. the kernel is 2.6.11 (taken from
> linux-mips.org) on Alchemy processor. This processor doesn't have
> performance counters. will it work on that ?

It should.

> 2. Also when i tried to see the kfi patch code. it doesn't talk about mips
> anywhere. but I happned to read somewhere on net that this patch works with
> mips also. what do you say about this ? what modifications do i need to do
> to make it work on mips ?

I didn't test the KFI for 2.6.11 patch on MIPS.  However, I have
patches against newer kernels (KFT on 2.6.14 and 2.6.16) which work
on the MIPS board I am using.  I didn't do anything special to
get the KFT patch working on MIPS.  Note that there are a few
MIPS-specific changes in the patch, including the addition
of the "__noinstrument" attribute on kernel_thread_helper
in arch/mips/kernel/process.c

Have you tried it and encountered a problem?  The tricky thing
with KFI (and KFT) is that it instruments ALL kernel functions.
Some functions don't work correctly when instrumented, but these
are very rare.  The usual symptom of it not working is that the
kernel will just hang on startup.  In one extreme case (ppc64),
I turned off instrumentation sub-system by sub-system (using compiler
flag switches in the Makefile), then by C file, then by function,
until I found the functions which needed to have the __noinstrument
attribute.

I hope this information is helpful.

Regards,
 -- Tim

=============================
Tim Bird
Architecture Group Chair, CE Linux Forum
Senior Staff Engineer, Sony Electronics
=============================