Hi! I'm new here so please forgive me if I'm being silly...
I am trying to use LTTng in order to pinpoint some some weird behaviours in a complex multi threaded application (e.g. unexplicable delays in the magnitude of hundreds of milliseconds) which appear under very unpredictable situations. I wish for an integraded user/kernel space tracing mechanism so to be able to measure latencies between known userspace markers, while knowing what the kernel is doing in the meantime. I am using a 2.6.33 kernel so I guess LTTng 2.x is not an option for me. I did something similar to http://lttng.org/files/usecases/LTTng-examples-siemens.pdf using custom unimplemented syscalls, which gives me interesting information in a very simple way, although I can only see the syscall number without its arguments (which would be very useful indeed). I saw a recent patch which addresses this but it's for LTTng 2.x so I don't think I can use it. I see how in past versions of LTTng there was ltt-usertrace: http://svn.lttng.org/svn/trunk/attic/ltt-usertrace/README which sortof does what I want (allow for tracepoint messages from user space by adding custom syscalls ltt_trace_generic and ltt_register_generic), but this seems deprecated somehow. *Could somebody please tell me what happened and why it was removed?* I know I have two alternatives: a) Writing messages to /mnt/debugfs/ltt/write_event, but I'm afraid this would add more uncertainty to the behaviour of the system - e.g., affect scheduling - due to the fact that I'm writing to a file (but maybe I am wrong). b) Use LTTng Userspace Tracer (UST), but I see two drawbacks: 1) Need to link in liburcu and change the startup command which is something I would rather avoid 2) The trace information would end up in a separate trace file and I really don't want to take the risk of having the kernel and user traces based on different timestamps. So could someone please shed some light? Thanks! Gerlando _______________________________________________ ltt-dev mailing list [email protected] http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
