linux-kernel - Re: [RFC PATCH 00/28] ktap: A lightweight dynamic tracing tool for Linux

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Message-ID: <20140331071749.GA1252@gmail.com>
Date:	Mon, 31 Mar 2014 09:17:49 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Jovi Zhangwei <jovi.zhangwei@...il.com>
Cc:	Ingo Molnar <mingo@...hat.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Daniel Borkmann <dborkman@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jiri Olsa <jolsa@...hat.com>
Subject: Re: [RFC PATCH 00/28] ktap: A lightweight dynamic tracing tool for
 Linux


* Jovi Zhangwei <jovi.zhangwei@...il.com> wrote:

> Hi All,
> 
> The following set of patches add ktap tracing tool. 
> 
> ktap is a new script-based dynamic tracing tool for Linux.
> It uses a scripting language and lets the user trace system dynamically.
> 
> Highlights features:
> * a simple but powerful scripting language
> * register-based interpreter (heavily optimized) in Linux kernel
> * small and lightweight
> * not depend on the GCC toolchain for each script run
> * easy to use in embedded environments without debugging info
> * support for tracepoint, kprobe, uprobe, function trace, timer, and more
> * supported in x86, ARM, PowerPC, MIPS
> * safety in sandbox

I've asked this fundamental design question before but got no full 
answer: how does ktap compare to the ongoing effort of improving the 
BPF scripting engine?

There's several efforts here that I'm aware of:

 1) 64-bit BPF, integration with ftrace scripting, see this lkml 
    thread:

    [RFC PATCH v2 tip 0/7] 64-bit BPF insn set and tracing filters

 2) better BPF integration with networking:

    [PATCH net-next v3 8/9] net: filter: rework/optimize internal BPF interpreter's instruction set

Your patches introduce a separate bytecode interpreter in 
kernel/trace/ktap/ and that's overlapping with BPF.

>From a long term instrumentation code maintenance point of view the 
last thing we want is several overlapping scripting engines.

Thanks,

	Ingo
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