It could be interesting to at least reserve the size for the first packet, so we have at least a little bit of information on the trace.
On 2012-11-16 10:29, David Goulet 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 :) > > 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 _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
