Re: [HACKERS] max_files_per_processes vs others uses of file descriptors

Andres Freund <andres@anarazel.de> writes:
> On 2017-08-07 17:30:13 -0400, Tom Lane wrote:
>> Meh.  The lack of field complaints about this doesn't indicate to me that
>> we have a huge problem, and in any case, just increasing NUM_RESERVED_FDS
>> would do nothing for the system-wide limits.

> Howso? Via count_usable_fds() we test for max_files_per_process /
> RLIMIT_NOFILE fds, and *then* subtract NUM_RESERVED_FDS.

The limit I'm worried about is the kernel's overall FD table size limit
(ENFILE failures), not the per-process limit.  PG has a well-known
propensity for eating the entire kernel table under heavy load.  We
wouldn't ever have bothered with those retry loops otherwise.
        regards, tom lane