Messages in this thread | | | Date | Mon, 26 Oct 2009 21:21:13 +0100 | From | Ingo Molnar <> | Subject | Re: Relicensing tracepoints and markers to Dual LGPL v2.1/GPL v2,headers to Dual BSD/GPL |
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* Arjan van de Ven <arjan@infradead.org> wrote:
> On Mon, 26 Oct 2009 09:17:49 -0400 > Pierre-Marc Fournier <pierre-marc.fournier@polymtl.ca> wrote: > > > Ingo Molnar wrote: > > > > > > But i also disagree with it on a technical level: code duplication > > > is _bad_. Why does the code have to be duplicated in user-space > > > like that? I'd like Linux tracing code to be in the kernel repo. > > > Why isnt this done properly, as part of the kernel project - to > > > make sure it all stays in sync? > > > > > > > If you mean that this code should solely be used inside the kernel, > > then what you propose technically does not work. There is a very high > > cost to accessing kernel code from userspace. > > yeah 100 cycles is insanely high, that's at least the equivalent of... > say one cache miss.
That too - plus 'being in the kernel repo' does not mean it has to run in kernel mode. It could be a vdso feature or a library in tools/. I'm quite sure it's a mistake to ad-hoc export the current tracepoint.c code to user-space without having it all under the same maintenance envelope.
Ingo
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