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Message-ID: <20060919191652.GC30556@Krystal>
Date: Tue, 19 Sep 2006 15:16:52 -0400
From: Mathieu Desnoyers <compudj@...stal.dyndns.org>
To: Vara Prasad <prasadav@...ibm.com>
Cc: Martin Bligh <mbligh@...gle.com>, prasanna@...ibm.com,
Andrew Morton <akpm@...l.org>,
"Frank Ch. Eigler" <fche@...hat.com>, Ingo Molnar <mingo@...e.hu>,
Paul Mundt <lethal@...ux-sh.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
Jes Sorensen <jes@....com>, Tom Zanussi <zanussi@...ibm.com>,
Richard J Moore <richardj_moore@...ibm.com>,
Michel Dagenais <michel.dagenais@...ymtl.ca>,
Christoph Hellwig <hch@...radead.org>,
Greg Kroah-Hartman <gregkh@...e.de>,
Thomas Gleixner <tglx@...utronix.de>,
William Cohen <wcohen@...hat.com>, ltt-dev@...fik.org,
systemtap@...rces.redhat.com, Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH] Linux Kernel Markers
* Vara Prasad (prasadav@...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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