LTTng » LTTng-tools

There is a design limitation of per-pid UST buffers when used in live mode which should be documented.

Basically, because the per-pid buffers are reclaimed soon after the application exits, it may cause the events traced by a short-lived application to never appear in the output of a live trace when per-pid buffers are used.

This is caused by the fact that the live client periodically checks for new buffers, but there is no inherent reference kept on the streams before they disappear.

This means that the information will be available in the disk output of the trace, but it will be missing from the live mode output.

This could eventually be mitigated by keeping references to the streams received by the relay daemon which are of interest to a live client until they are referenced by the live client.