Re: [PATCH] Linux Kernel Markers

Mathieu Desnoyers
2006-09-19T19:22:07Z

* 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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