[Libguestfs] Long running nbdkit instances seem to leak memory

[Richard W.M. Jones]

I'm using nbdkit + the file plugin to serve NBD root filesystems for
some machines, so I get to observe how it behaves for very long runs.
I think this indicates a memory leak?

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
 5038 root      20   0 4577220  16000    796 S   0.0  0.1  30:52.40 nbdkit
 5592 root      20   0 4159224  11708    784 S   0.0  0.1  22:21.67 nbdkit

Not sure how to easily diagnose this.  My thought was to force a
coredump by sending a signal, but I don't know if these processes have
a suitable rlimit.  I could also attach gdb.  Perhaps by looking at a
dump of the memory we could get an idea of what structure leaks.

Unfortunately also it's a very old version:

$ rpm -qf /usr/sbin/nbdkit 
nbdkit-1.8.0-1.el7.x86_64

Rich.

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