Re: [PATCH -tip v5 4/7] tracing: add kprobe-based event tracer

[Christoph Hellwig <hch@infradead.org>]

On Fri, May 08, 2009 at 08:48:59PM -0400, Masami Hiramatsu wrote:
> 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).

That's some pretty cool functionality, especially together with patch 7.

But as with so many tracing bits in the kernel it's just lowlevel bits
without a good user interface.  We'd really need some high-level way
for sysadmins/developers to use it.  E.g. a version of the systemtap
compiler that doesn't build a kernel module but instead uses the event
tracer + the kprobes tracer.

Or a model like Tom's zedtrace where a perl script would do the dwarf
lookups and generates these probes in addition to the filtered event
traces.