Re: Problems raising fd limits in 1.3.78-1.3.80

Stephen Tweedie (
Tue, 2 Apr 1996 16:44:36 +0100


In article <>,
David ``Joel Katz'' Schwartz <> writes:

> On Mon, 1 Apr 1996 wrote:
>> It is not recommended to increase __FD_SET's size. Unfortunately,
>> however large you make it, libc simply cannot cope with a select size
>> larger than 256 fd's.

> Libc doesn't have to do anything. I just need the fdset macros to
> work and I need select to work.

Yup. I wonder if it's worth upping the limit in libc (as exported by
linux/fs.h) to 1024 anyway? It only really affects the size of the
fd_set, so it doesn't cost much. It ought to be pretty easy to make
the kernel's maximum fd number configurable, with processes inheriting
the current default value on fork() (we probably don't want to change
the fd table size dynamically on existing processes).


Stephen Tweedie <>
Department of Computer Science, Edinburgh University, Scotland.