[lttng-dev] Google Summer of Code

Thibault, Daniel Daniel.Thibault at drdc-rddc.gc.ca
Thu Apr 11 09:20:55 EDT 2013

De : jeremie.galarneau at gmail.com [mailto:jeremie.galarneau at gmail.com] De la part de Jérémie Galarneau
Envoyé : 10 avril 2013 17:53

Certainly seems worthwhile to me although I never heard about debugfs being phased out. Could you clarify that point?


> On Tue, Apr 9, 2013 at 11:21 AM, Thibault, Daniel <Daniel.Thibault at drdc-rddc.gc.ca<mailto:Daniel.Thibault at drdc-rddc.gc.ca>> wrote:
>   Even if the debugfs tracing facility is destined for eventual withdrawal from the Linux kernel, it may be of interest to some to recover older traces generated in this way -if only in order to be able to process them in the same way as CTF text dumps.  Conversion to the babeltrace text format should be fairly straightforward; conversion to CTF would be trickier.

   Pure speculation on my part, based on the observation that the debugfs service seems less efficient than lttng.  The sentence is meant to be read "this may be of interest even if debugfs turns out to be destined to be phased out".  (I'd like to know whether the debugfs facility is as signal-, thread-, and interrupt-safe as lttng)

   This said, do you know more about how this facility came about?  LTTng 1 used debugfs for its trace control as well, so which came first?  Debugfs or lttng 1?  How come the tracepoint and syscall tracing achievable with debugfs is not a perfect match with lttng's (re lttng 2)?  (lttng traces the kvm, lttng_statedump, and snd_soc subsystems but debugfs does not; conversely, lttng misses the drm, fs, mce, raw_syscalls, vfs, vsyscall, and xen subsystems; on the syscall side, lttng captures sys_clone, sys_execve and sys_unknown (which debugfs misses), while I haven't found debugfs syscalls that lttng misses (but I can't rule out that possibility))

Daniel U. Thibault
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