[lttng-dev] Deleted files held open by LTTng

[nils.doering at fujitsu.com]

Hi all,

I have recently started using LTTng and stumbled upon the fact, that
LTTng is keeping a lot of open file pointers to a single deleted file.

Specifically the process that holds these open is the lttng-consumerd and its
threads. The file that is held open, but is deleted is
/dev/shm/ust-shm-consumer-${PID} with the PID of the lttng-comsumerd. The
number of open file descriptors is dependent on the number of CPUs the
system has and results to 16 + (#CPUs * 16). Is this behavior expected?

# lsof | grep lttng | grep DEL
lttng-con  2280             root  DEL       REG               0,18               11128
        /dev/shm/ust-shm-consumer-2280
lttng-con  2280             root  DEL       REG               0,18               11127
        /dev/shm/ust-shm-consumer-2280
lttng-con  2280             root  DEL       REG               0,18               11126
        /dev/shm/ust-shm-consumer-2280
[...]

I have tested this on a Xen-Dom0 system running SLES 12 SP5 and on a
SLES12 SP5 without Xen.

Best regards,
Nils Döring