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Date: Thu, 27 Aug 2009 09:31:39 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
       Masami Hiramatsu <mhiramat@redhat.com>, Avi Kivity <avi@redhat.com>,
       Andi Kleen <ak@linux.intel.com>, Christoph Hellwig <hch@infradead.org>,
       "Frank Ch. Eigler" <fche@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
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       Steven Rostedt <rostedt@goodmis.org>, Tom Zanussi <tzanussi@gmail.com>,
       Vegard Nossum <vegard.nossum@gmail.com>
Subject: Re: [PATCH 08/18] tracing: Add kprobe-based event tracer
Message-ID: <20090827073139.GB2131@elte.hu>
References: <1251340337-5640-1-git-send-email-fweisbec@gmail.com> <1251340337-5640-9-git-send-email-fweisbec@gmail.com>
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* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> From: Masami Hiramatsu <mhiramat@redhat.com>
> 
> 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).
> 
> Similar to the events tracer, this tracer doesn't need to be 
> activated via current_tracer, instead of that, just set probe 
> points via /sys/kernel/debug/tracing/kprobe_events. And you can 
> set filters on each probe events via 
> /sys/kernel/debug/tracing/events/kprobes/<EVENT>/filter.

ok, one observation here: this should seemlessly merge into 
/debug/tracing/events/ and provide a record format descriptor in 
'format' to allow the automated fetching of the results of the 
probe. The PERF_SAMPLE_RAW gateway should work as well.
 
That way tooling that knows about /debug/tracing/events/ will 
automatically work with kprobes events as well. We can profile based 
on kprobes, etc. etc.

The _setting_ of the probe is still a separate channel - but if 
existing installed probes are merged into existing tooling that's a 
big step forward in terms of utility.

	Ingo