Re: [PATCH] Linux Kernel Markers

[Mathieu Desnoyers <compudj@krystal.dyndns.org>]

* Vara Prasad (prasadav@us.ibm.com) wrote:
> Martin Bligh wrote:
> 
> >[...]
> >Depends what we're trying to fix. I was trying to fix two things:
> >
> >1. Flexibility - kprobes seem unable to access all local variables etc
> >easily, and go anywhere inside the function. Plus keeping low overhead
> >for doing things like keeping counters in a function (see previous
> >example I mentioned for counting pages in shrink_list).
> >
> Using tools like systemtap on can consult DWARF information and put 
> probes in the middle of the function and access local variables as well, 
> that is not the real problem. The issue here is compiler doesn't seem to 
> generate required DWARF information in some cases due to optimizations.  
> The other related problem is when there exists debug information, the 
> way to specify the breakpoint location is using line number which is not 
> maintainable, having a marker solves this problem as well. Your proposal 
> still doesn't solve the need for markers if i understood correctly.
> 

His implementation makes a heavy use of a marker mechanism : this is exactly
what permits to create the instrumented objects from the same source code, but
with different #defines.

Mathieu
 
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