[Linux-ia64] Re: pfmon with kernel 2.5.35?

From: Stephane Eranian <eranian_at_frankl.hpl.hp.com>
Date: 2002-09-21 03:03:08
Bonjour Jean-Francois,


On Fri, Sep 20, 2002 at 12:30:18PM +0200, lemerrjf wrote:
> I have tried pfmon on a Tiger machine with 4 CPUs.
> it works pretty well on a kernel 2.4.18
> 
> However on a kernel 2.5.35, I obtain, with the command
> 
> pfmon --system-wide
> 
> Thread does not run on correct CPU: 0 instead of 1
> Thread does not run on correct CPU: 0 instead of 2
> Thread does not run on correct CPU: 0 instead of 3
> 
> I observe the same problem with other kernels adding the
> "multiple run queue" functionnalities.
> 
> Have you observed the same problem?

Obviously this has not been tested with 2.5.x. Keep in mind
that this is a development (unstable) kernel. 

The problem is not in the kernel but in pfmon. The routine
that retrieves the current CPU is bogus. From 2.4.x to 2.5.x
the content of /proc/pid/stat has changed and this exposed
a bug in pfmon/pfmon_util.c:find_cpu(). The thread is indeed
running on the right CPU. 

You can apply the attached patch to pfmon-1.1 to fix 
the problem with pfmon. Note that this fix works for both
2.4.x and 2.5.x

Thanks for finding this problem.

-- 
-Stephane



Received on Fri Sep 20 10:05:35 2002

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