Re: Re: Too many open files (was Re: spinlock problems reported earlier)

The Hermit Hacker <scrappy(at)hub(dot)org> writes:
>> cat t.c
> #include <stdio.h>
> #include <unistd.h>

> main()
> {
> printf("%ld\n", sysconf(_SC_OPEN_MAX));
> }

>> ./t
> 4136

Yup, there's our problem. Each backend will feel entitled to open up to
about 4100 files, assuming it manages to hit that many distinct tables/
indexes during its run. You probably haven't got that many, but even
several hundred files times a couple dozen backends would start pushing
your (previous) kernel FD limit.

So, at least on FreeBSD, we can't trust sysconf(_SC_OPEN_MAX) to tell us
the number we need.

An explicit parameter to the postmaster, setting the installation-wide
open file count (with default maybe about 50 * MaxBackends) is starting
to look like a good answer to me. Comments?

regards, tom lane