Re: [PATCH] markers-linker-generic

Frank Ch. Eigler
2007-04-11T23:00:01Z

Andrew Morton <akpm@linux-foundation.org> writes:

> [...] I am told that the systemtap developers plan to (or are)
> using this infrastructure.

Indeed.

> If correct: what is their reason for preferring it over kprobes?
> [...]

It's not a preference - it's more of a supplement. It's helpful when
some combination of such factors exists:

- kprobe int3-fault dispatching overhead orders of magnitude too high
- fault dispatching not permissible in some areas
- local context variables not easily retrievable via dwarf information
- dwarf information not available at all
- costs of permanently placed but passive marker acceptable

>From systemtap's point of view, instrumentation hooked to markers,
kprobes, and other facilities like timers, coexist just fine. A
greater number of probe-able event sources makes for a richer tool.

- FChE