linux-kernel - Re: [RFC PATCH tip 4/5] use BPF in tracing filters

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Message-ID: <y0m38m3qk23.fsf@fche.csb>
Date:	Sun, 08 Dec 2013 13:22:44 -0500
From:	fche@...hat.com (Frank Ch. Eigler)
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Jovi Zhangwei <jovi.zhangwei@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tom Zanussi <tom.zanussi@...ux.intel.com>,
	Eric Dumazet <edumazet@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"yrl.pp-manager.tt@...achi.com" <yrl.pp-manager.tt@...achi.com>
Subject: Re: [RFC PATCH tip 4/5] use BPF in tracing filters


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
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