[Virtio-fs] Large memory consumption by virtiofsd, suspecting fd's aren't being closed?

[Eric Ernst]

Hey ya’ll,

One challenge I’ve been looking at is how to setup an appropriate memory
cgroup limit for workloads that are leveraging virtiofs (ie, running pods
with Kata Containers that leverage virtiofs). I noticed that memory usage
of the daemon itself can grow considerably depending on the workload;
though much more than I’d expect.

I’m running workload that simply runs a build on kernel sources with -j3.
In doing this, the source of the linux kernel are shared via virtiofs (no
DAX), so as the build goes on, there are a lot of files opened, closed, as
well as created. The rss memory of virtiofsd grows into several hundreds of
MBs.

When taking a look, I’m suspecting that virtiofsd is carrying out the
opens, but never actually closing fds. In the guest, I’m seeing fd’s on the
order of 10-40 for all the container processes as it runs, whereas I see
the number of fds for virtiofsd continually increasing, reaching over
80,000 fds. I’m guessing this isn’t expected?

Can any ya’ll help shed some light, or where I can look?

Thanks,
Eric
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