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To: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Jovi Zhangwei <jovi.zhangwei@gmail.com>,
        Alexei Starovoitov <ast@plumgrid.com>,
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        LKML <linux-kernel@vger.kernel.org>,
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Subject: Re: [RFC PATCH tip 4/5] use BPF in tracing filters
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From: fche@redhat.com (Frank Ch. Eigler)
Date: Sun, 08 Dec 2013 13:22:44 -0500
In-Reply-To: <52A26268.5070403@hitachi.com> (Masami Hiramatsu's message of "Sat, 07 Dec 2013 08:48:56 +0900")
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masami.hiramatsu.pt wrote:

> [...]
> Anyway, as far as I can see, there looks be two different models of
> tracing in our mind.
>
> A) Fixed event based tracing: In this model, there are several fixed
> "events" which well defined with fixed arguments. tracer handles these
> events and only use limited arguments. It's like a packet stream
> processing. ftrace, perf etc. are used this model.
>
> B) Flexible event-point tracing: In this model, each tracer(or even
> trace user) can freely define their own event, there will be some fixed
> tracing points defined, but arguments are defined by users. It's like a
> debugger's breakpoint debugging. systemtap, ktap etc. are used this model.

It may be more useful to think of it as a contrast along the
hard-coded versus programmable axis.  (perf, systemtap, and ktap can
each reach to some extent across your "fixed" vs "flexible" line.
Each has some dynamic and some static-tracepoint capability.)


> e.g. B model has a good flexibility and A model is easy to use for
> beginners.

I don't think it's the model that dictates ease-of-use, but the
quality of implementation, logistics, documentation, and examples.


- FChE