Messages in this thread | | | Date | Fri, 15 Sep 2006 00:15:21 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 0/11] LTTng-core (basic tracing infrastructure) 0.5.108 |
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* Roman Zippel <zippel@linux-m68k.org> wrote:
> Hi, > > On Thu, 14 Sep 2006, Daniel Walker wrote: > > > > Ingo, so far you have made not a single argument why they can't coexist > > > except for your personal dislike. > > > > Not to put to fine a point on it, but I think there's not a small number > > of us that "prefer" the best solution. > > You can have it. > OTOH I would also like to know what's going in my m68k kernel without > having to implement some rather complex infrastructure, which I don't > need otherwise. There hasn't been a single argument so far, why we > can't have both.
the argument is very simple: LTT creates strong coupling, it is almost a set of 350+ system-calls, moved into the heart of the kernel. Once moved in, it's very hard to remove it. "Why did you remove that trace information, you broke my LTT script!"
While with SystemTap the coupling is alot smaller. With dynamic tracing there's no _fundamental requirement_ for _any_ tracepoint to be in the source code, hence we have the present and future flexibility to eliminate most of them. So my point is: shape all the static tracepoints in a "provide data to dynamic tracers" way. If they are removed (which we should have the freedom to do), the removal is not a showstopper.
Flexibility of future choices, especially for user/developer-visible features, is one of the most important factors of kernel maintainance.
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