[lttng-dev] Large number of stream files in CTF trace -- too many file handles

Rocky Dunlap dunlap at ucar.edu
Mon Mar 16 23:38:11 EDT 2020


Increasing the soft FD limit worked great, both for the command line and
the Python script.  Thanks for the help!


On Mon, Mar 16, 2020 at 8:51 AM Jonathan Rajotte-Julien <
jonathan.rajotte-julien at efficios.com> wrote:

> Hi,
> > If this is not the right approach, how should I proceed?  E.g., should
> the
> > source-ctf-fs manage a limited pool of file handles?  I would think this
> > would be pretty inefficient as you would need to constantly open/close
> > files--expensive.
> I would probably start looking at the soft and hardlimit for the
> babeltrace2
> process in terms of open file:
> On my machine:
> joraj@~[]$ ulimit -Sn
> 1024
> joraj@~[]$ ulimit -Hn
> 1048576
> That is a lot of headspace.
> I might have a setting somewhere increasing the base hardlimit but
> in any case you will see how much room you have.
> Based on the number of streams you have, I would say that you will
> need more than 2000 as a base soft limit for this trace.
> We do have a FD pooling system in place in another project we maintain
> (lttng-tools[1] GPL-2.0) that might be pertinent for babeltrace2 at some
> point
> in time. As for the overhead that would occur in a scenario with not
> enough FD
> available, I think it is a good compromise between either reading a trace
> or
> not reading it at all. A warning informing the user that we reached
> the limit of the pool might be a good start in such case.
> [1] https://github.com/lttng/lttng-tools/tree/master/src/common/fd-tracker
> Cheers
> --
> Jonathan Rajotte-Julien
> EfficiOS
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.lttng.org/pipermail/lttng-dev/attachments/20200316/66238df5/attachment.htm>

More information about the lttng-dev mailing list