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

[Ingo Molnar <mingo@kernel.org>]

* Jovi Zhangwei <jovi.zhangwei@gmail.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