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Re: PATCH: Turn on -fomit-frame-pointer by default for 32bit Linux/x86


On Wed, 4 Aug 2010, Andi Kleen wrote:

> > Can we find if oprofile works with -fomit-frame-pointer on 32bit Linux/x86.
> 
> It doesn't for user space. The problem is that you would need
> an in kernel dwarf2 unwinder that reads user space tables. 
> 
> x86-64 suffers from this already.
> 
> However there are some alternative approaches being explored for this,
> like using LBRs. 

 I don't know what a LBR is, but FWIW, it looks to me like a scenario 
asking for a userspace daemon interpreting raw address/stack information 
passed on from the kernel.  The daemon could use whatever complex tools 
are needed to interpret the information received or just dump it somewhere 
in a form complete enough for later post-processing (e.g. if the tools 
required were not fast enough to cope in real time).

 Just because while in some cases it seems easier to code (hack) things 
into the kernel, it does not necessarily mean they should be there.  The 
fewer things in the kernel the better.  Just IMHO.

  Maciej


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