Comment 5 for bug 1720887

We have at least to think if infinity is the right value before changing it (and if we change we want to push it upstream, so consideration thought are useful in any case).

Obviously it removes it being a blocker for many guests, but OTOH it is meant to avoid overloads of the system.

The current limit (default) is 8192 (read from /proc/<pid>/limits of the process.
It starts with a base of about 15 and adds 1 per guest.
That would make me expect being a limit short of 8k guests which for a single host is high enough that I'd agree to an admin having to opt in changing a conffile.

But you reported that your cases break around 250 which should be working IMHO.

The comments in the upstream .service file already kind of support my theory that the number should be sufficient.
# Need to have at least one file open per guest (eg QEMU
# stdio log), but might be more (eg serial console logs)
# libvirtd.service written to expect 4096 guests, so if we
# guess at 2 log files per guest here (stdio + 1 serial):
LimitNOFILE=8192

But that also means that if you have many serials by default, then you'll exceed it much faster.
Never the less to break around 250 you'd need 32 serials per guest which seems a bit too much right?