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Re: [PATCH] Linux Kernel Markers
- From: Mathieu Desnoyers <compudj at krystal dot dyndns dot org>
- To: Vara Prasad <prasadav at us dot ibm dot com>
- Cc: "Martin J. Bligh" <mbligh at google dot com>, Ingo Molnar <mingo at elte dot hu>, "Frank Ch. Eigler" <fche at redhat dot com>, Paul Mundt <lethal at linux-sh dot org>, linux-kernel <linux-kernel at vger dot kernel dot org>, Jes Sorensen <jes at sgi dot com>, Andrew Morton <akpm at osdl dot org>, Tom Zanussi <zanussi at us dot ibm dot com>, Richard J Moore <richardj_moore at uk dot ibm dot com>, Michel Dagenais <michel dot dagenais at polymtl dot ca>, Christoph Hellwig <hch at infradead dot org>, Greg Kroah-Hartman <gregkh at suse dot de>, Thomas Gleixner <tglx at linutronix dot de>, William Cohen <wcohen at redhat dot com>, ltt-dev at shafik dot org, systemtap at sources dot redhat dot com, Alan Cox <alan at lxorguk dot ukuu dot org dot uk>
- Date: Tue, 19 Sep 2006 13:43:57 -0400
- Subject: Re: [PATCH] Linux Kernel Markers
- References: <20060918234502.GA197@Krystal> <20060919081124.GA30394@elte.hu> <451008AC.6030006@google.com> <45101598.7050309@us.ibm.com>
* Vara Prasad (prasadav@us.ibm.com) wrote:
> It is an interesting idea but there appears to be following hard issues
> (some of which you have already listed) i am not able to see how we can
> overcome them
>
> 1) We are going to have a duplicate of the whole function which means
> any significant changes in the original function needs to be done on the
> copy as well, you think maintainers would like this double work idea.
>
Not with my marker proposal. There is only need to compile it with different
flags.
> 2) Inline functions is often the place where we need a fast path to
> overcome the current kprobes overhead.
>
> 3) As you said it is not trivial across all the platforms to do a switch
> to the instrumented function from the original during the execution.
> This problem is similar to the issue we are dealing with djprobes.
>
I would really like to know how good djprobes is at instrumenting the
prologue of a function.
Mathieu
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