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Date: Mon, 11 May 2009 05:32:24 -0400
From: Christoph Hellwig <hch@infradead.org>
To: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
       lkml <linux-kernel@vger.kernel.org>,
       systemtap <systemtap@sources.redhat.com>, kvm <kvm@vger.kernel.org>,
       Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
       Frederic Weisbecker <fweisbec@gmail.com>,
       Tom Zanussi <tzanussi@gmail.com>
Subject: Re: [PATCH -tip v5 4/7] tracing: add kprobe-based event tracer
Message-ID: <20090511093224.GC23875@infradead.org>
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On Fri, May 08, 2009 at 08:48:59PM -0400, Masami Hiramatsu wrote:
> Add kprobes based event tracer on ftrace.
> 
> This tracer is similar to the events tracer which is based on Tracepoint
> infrastructure. Instead of Tracepoint, this tracer is based on kprobes(kprobe
> and kretprobe). It probes anywhere where kprobes can probe(this means, all
> functions body except for __kprobes functions).

That's some pretty cool functionality, especially together with patch 7.

But as with so many tracing bits in the kernel it's just lowlevel bits
without a good user interface.  We'd really need some high-level way
for sysadmins/developers to use it.  E.g. a version of the systemtap
compiler that doesn't build a kernel module but instead uses the event
tracer + the kprobes tracer.

Or a model like Tom's zedtrace where a perl script would do the dwarf
lookups and generates these probes in addition to the filtered event
traces.