linux-kernel - Re: sysprof in 2.6.27 kernel

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Date:	16 Aug 2008 05:16:34 +0200
From:	Soeren Sandmann <sandmann@...mi.au.dk>
To:	Lukas Hejtmanek <xhejtman@....muni.cz>
Cc:	linux-kernel@...r.kernel.org, mingo@...hat.com
Subject: Re: sysprof in 2.6.27 kernel

Soeren Sandmann <sandmann@...mi.au.dk> writes:

> Lukas Hejtmanek <xhejtman@....muni.cz> writes:
> 
> > On Thu, Aug 14, 2008 at 01:23:16AM +0200, Soeren Sandmann wrote:
> > > It's somewhat rough still. If you try it out, I will be interested in
> > > any feedback you have.
> > 
> > another feedback. I got No map at all processes even at those I got debug info
> > installed.
> 
> This may be because sysprof user space is not running as root, or it
> may be because the kernel is generating bogus addresses. 
> 
> Generally, "No Map" means sysprof is seeing samples in memory regions
> that are not in /proc/<pid>/maps

Actually, I seem to remember one cause of this: the vdso code creates
an unusual stackframe where the pointer to the previous frame is
stored in an unusual place. I think the sysprof kernel code needs to
take this into account, or alternatively send sufficient information
to userspace that it can figure it out itself.


Soren
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