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Re: Porting "jump labels" to userspace (was: Re: [ltt-dev] LTTng-UST vs SystemTap userspace tracing benchmarks)
- From: Roland McGrath <roland at redhat dot com>
- To: Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>
- Cc: Mark Wielaard <mjw at redhat dot com>, Stefan Hajnoczi <stefanha at gmail dot com>, "Frank Ch. Eigler" <fche at redhat dot com>, Julien Desfossez <julien dot desfossez at polymtl dot ca>, dominique dot toupin at ericsson dot com, ltt-dev at lists dot casi dot polymtl dot ca, systemtap at sources dot redhat dot com, linux-kernel at vger dot kernel dot org, Jason Baron <jbaron at redhat dot com>, hpa at zytor dot com, rostedt at goodmis dot org, mingo at elte dot hu, tglx at linutronix dot de, andi at firstfloor dot org, rth at redhat dot com, masami dot hiramatsu dot pt at hitachi dot com, fweisbec at gmail dot com, avi at redhat dot com, davem at davemloft dot net, sam at ravnborg dot org, ddaney at caviumnetworks dot com, michael at ellerman dot id dot au, Peter Zijlstra <peterz at infradead dot org>
- Date: Wed, 16 Feb 2011 12:04:49 -0800 (PST)
- Subject: Re: Porting "jump labels" to userspace (was: Re: [ltt-dev] LTTng-UST vs SystemTap userspace tracing benchmarks)
- References: <4D5AA164.1050607@polymtl.ca> <y0mvd0ltgba.fsf@fche.csb> <AANLkTi=Nsy6fXE9=Njxs9LPHuohHzf=q5kD+fK765Rht@mail.gmail.com> <1297853778.3224.90.camel@springer.wildebeest.org> <20110216185056.CAD7B1806E0@magilla.sf.frob.com> <20110216200034.GA6066@Krystal>
IMHO there is not really so much to the in-kernel implementation that it's
worth attempting to reuse the code in userland. Pretty much all the work
is in the details of the implementation that would naturally differ a lot
in a different context. If you understand the mechanism and the machine
details, then implementing it well for a userland context is not a big deal
and is cleaner to do from scratch than shoe-horning kernel-centric code
into a wildly different context.
Thanks,
Roland