Re: [PATCH] Linux Kernel Markers

[Karim Yaghmour <karim@opersys.com>]

Hello Frank,

Frank Ch. Eigler wrote:
> My interpretation of Martin's Monday proposal is that, if implemented,
> we wouldn't need any of this nop/int3 stuff.  If function being
> instrumented were recompiled on-the-fly, then it could sport plain &
> direct C-level calls to the instrumentation handlers.

Absolutely. I guess the length of these threads is just fertile
ground for misunderstandings. Basically what Hiramatsu-san and
myself were discussing was just the mechanism for selecting/
forking in between the uninstrumented function and the instrumented
one.

So, to recap:

If you had 100,000 instrumentation points in the scheduler (obviously
a totally bogus number here ...) you'd have 2 functions:
1- one with no instrumentation at all, but with a 5byte filler such
   as the one presented by Hiramatsu-san.
2- one with the instrumentation.

Early in the proposal, the mechanics of switching in between "1" and "2"
seemed to be problematic, but I think with Hiramatsu-san's proposal
and, on the x86, djprobes, we've got it figured out.

Let me know if I'm not providing enough detail.

Thanks,

Karim