I added a "cat /proc/meminfo | grep Slab" to go-lxc-run.sh and found
this:

$ sysctl fs.inotify
fs.inotify.max_queued_events = 65536
fs.inotify.max_user_instances = 1024
fs.inotify.max_user_watches = 524288
$ ulimit -a
...
open files                      (-n) 1048576
...
$ go-lxc-run.sh
[0] x-001:[13]......7    Slab:             432176 kB
...
[1365] x-071:[15].......8    Slab:            9639484 kB
[1387] x-072:[15].......8    Slab:            9603648 kB
[1409] x-073:[14].......8    Slab:            9621936 kB
[1431] x-074:[14].......8    Slab:            9673000 kB
[1453] x-075:[13]........9    Slab:            9680444 kB
[1475] x-076:[14]........9    Slab:            8223312 kB
[1501] x-077:[16]......7    Slab:            5095880 kB
...
1812] x-093:[12]......7    Slab:            6163512 kB
[1831] x-094:[12]......7    Slab:            6271272 kB
[1850] x-095:[13]..................false    Slab:            6371956 kB
x-095 failed to boot. keeping x-095.

So kernel memory seemed to peak at around 10GB, and then somehow dropped
down to 5GB to allow 20 more containers to be created. (on a 16GB
machine, that's a fair bit allotted to just the kernel).

However, 95 seems to be the limit for 1024
fs.inotify.max_user_instances. But that still means setting it to 1M is
silly. I'll do another run with max_user_instances=2048 and see what
happens. Since I know with very-high max values, I can get to 230
containers, that sounds like 2048 is sufficient for it.

I'll also play around next with putting Juju into the loop and see where
I get. I really wonder about max-open-files for Root vs User. LXD is
running as Root, but if the containers are all running User level,
shouldn't that be the constraint?

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https://bugs.launchpad.net/bugs/1602192

Title:
  when starting many LXD containers, they start failing to boot with
  "Too many open files"

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