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Auto-tuning threshold discussions aside, it turns out that if you want to lower this on say, rather memory-packed machines, you either set maxusers or kern.maxfiles, or you set it in sysctl. The former is a non-exact way to tune this; the latter doesn't actually affect anything in the startup scripts. This first occured because I wondered why the hell screen would take upwards of 10 seconds to spawn a new screen. I then found python doing the same thing during fork/exec of child processes - it calls close() on each FD up to the current openfiles limit. On a 1TB machine this is like, 26 million FDs per process. Ugh. So: * This allows it to be set early in /boot/loader.conf; * It can be used to work around the ridiculous situation of screen, python, etc doing a close() on potentially millions of FDs even though you only have four open. Tested: * 4GB, 32GB, 64GB, 128GB, 384GB, 1TB systems with autotune, ensuring screen and python forking doesn't result in some pretty hilariously bad behaviour. TODO: * Note that the default login.conf sets openfiles-cur to unlimited, effectively obeying kern.maxfilesperproc. Perhaps we should fix this. * .. and even if we do, we need to also ensure that daemons get a soft limit of something reasonable and capped - they can request more FDs themselves. MFC after: 1 week Sponsored by: Norse Corp, Inc.
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