* David Goulet ([email protected]) wrote: > Hi Paul, > > The problem here would be that metadata can grow arbitrarily over time > when let say new events are enabled during tracing or a new lib is > dynamically loaded in the application you are tracing. Same goes for the > kernel for loaded module or CPU hotplug... > > To achieve a static size of metadata during the whole life of a tracing > session, I guess we need somekind of flag or option set to tell the > tracers to just deny new events once started... which from there, we > need Mathieu's opinion :)
live support will eventually allow to side-track this whole issue by flushing metadata to disk periodically during tracing, Thanks, Mathieu > > Cheers! > David > > Woegerer, Paul: > > Hi, > > > > embedded users sometimes have to trace to tmpfs (e.g. streaming in not > > an option due to missing network connectivity). > > > > Ramdisks of 16M to 128M size are created and as long as the ram disk > > does not get full, tracing works fine. Unfortunately if the disk gets > > full things fall apart: > > > > PERROR: Error in file write: No space left on device [in > > lttng_consumer_on_read_subbuffer_mmap() at consumer.c:1367] > > > > The consumer daemon will not be able to write the metadata channel and > > therefore the trace data set will be unusable (cannot be read with > > babeltrace). > > > > -rwxrwxrwx 1 testuser users 0 Nov 16 11:22 metadata > > -rwxrwxrwx 1 testuser users 15728640 Nov 16 11:22 myevents_0 > > -rwxrwxrwx 1 testuser users 4096 Nov 16 11:22 myevents_1 > > > > Is it possible to somehow reserve the file size (fallocate) for metadata > > so that in case the disk gets full at least the metadata gets written > > and the resulting trace set is readable with babeltrace ? > > > > I wonder if that is possible at all. The consumer daemon doesn't know > > upfront how much would need to be reserved for metadata, right ? > > > > Any ideas ? > > > > Thanks, > > Paul > > > > > > _______________________________________________ > lttng-dev mailing list > [email protected] > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
