Re: Trying to get an embedded C function to use file I/O

[Jeff Johnston <jjohnstn at redhat dot com>]

Thanks Frank.  I think option b sounds most promising as they
separate per-cpu data and so I think I'll let SystemTap do that work.

-- Jeff J.

----- Original Message -----
From: "Frank Ch. Eigler" <fche@redhat.com>
To: "Jeff Johnston" <jjohnstn@redhat.com>
Cc: systemtap@sourceware.org
Sent: Monday, August 19, 2013 6:02:12 PM
Subject: Re: Trying to get an embedded C function to use file I/O


jjohnstn wrote:

> [...]  The LTTng kernel side of the trace ends up with multiple CTF
> format files: a metadata file which describes the data format and a
> number of binary files (essentially a permutation of CPUs and
> channels (usually just channel 0). [...]

Is lttng restricted to having only a single 'channel' or dataset per
file?  If not, why not 

(a) have one monster CTF file that includes cross-cpu cross-channel
    cross-everything data?
or
(b) use stap -b (bulk) mode to produce per-cpu files, each of which
    could be converted to CTF in userspace (perhaps requiring nothing
    but removal of the stap timestamping/framing metadata in those
    bulk-mode files; see stap-merge.c).

- FChE