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Re: [PATCH] Linux Kernel Markers 0.5 for Linux 2.6.17 (with probe management)
- From: Christoph Hellwig <hch at infradead dot org>
- To: Mathieu Desnoyers <compudj at krystal dot dyndns dot org>
- Cc: Ingo Molnar <mingo at elte dot hu>, Martin Bligh <mbligh at google dot com>, "Frank Ch. Eigler" <fche at redhat dot com>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, prasanna at in dot ibm dot com, Andrew Morton <akpm at osdl dot org>, 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>, 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: Fri, 22 Sep 2006 15:31:02 +0100
- Subject: Re: [PATCH] Linux Kernel Markers 0.5 for Linux 2.6.17 (with probe management)
- References: <20060921160009.GA30115@Krystal> <20060921160656.GA24774@elte.hu> <20060921214248.GA10097@Krystal>
I hate AOL-style me-toos, but there's nothing to add to this mail.
Thanks for this coherent writeup Mathieu.
On Thu, Sep 21, 2006 at 05:42:48PM -0400, Mathieu Desnoyers wrote:
> Hi Ingo,
>
> I clearly expressed my position in the previous emails, so did you. You argued
> about a use of tracing that is not relevant to my vision of reality, which is :
>
> - Embedded systems developers won't want a breakpoint-based probe
> - High performance computing users won't want a breakpoint-based probe
> - djprobe is far away from being in an acceptable state on architectures with
> very inconvenient erratas (x86).
> - kprobe and djprobe cannot access local variables in every cases
>
> For those reasons, I prefer a jump-over-call approach which lets gcc give us the
> local variables. No need of DWARF or SystemTAP macro Kung Fu. Just C and a
> loadable module.
>
> By no means is it a replacement for a completely dynamic breakpoint-based
> instrumentation mechanism. I really think that both mechanism should coexist.
>
> This is my position : I let the distribution/user decide what is appropriate for
> their use. My goal is to provide them a flexible mechanism that takes the
> multiple variety of uses in account without performance impact if they are not
> willing to pay it to benefit from tracing.
>
> With all due respect, yes, there are Linux users different from the typical
> Redhat client. If your vision is still limited to this scope after a 500
> emails debate, I am afraid that there is very little I can do about it in
> one more.