On Tue, Jan 06, 2004 at 09:53:47AM -0500, Brian Akins wrote:
> Call me stupid, put why in various places does Apache do things like this:
> if (csd >= FD_SETSIZE) {
> ap_log_error(APLOG_MARK, APLOG_WARNING, 0, NULL,
> "new file descriptor %d is too large; you probably
> need "
> "to rebuild Apache with a larger FD_SETSIZE "
> "(currently %d)",
> csd, FD_SETSIZE);
> apr_socket_close(sock);
> return;
> }
>
> On linux, at least, FD_SETSIZE is fairly low (1024), yet the actually
> max file descriptors can be much, much higher (we have thousands per
> process with squid).
>
> Is this just not true elsewhere? Can someone explain?
You can use file descriptors up to OPEN_MAX.
However, you can only select() on fds < FD_SETSIZE.
That is a limitation of select() because of the memory size
of the fd_set typedef (based on FD_SETSIZE).
It is not a limitation of poll(), or other mechanisms like
kqueue, sys_epoll, or /dev/poll.
Cheers,
Glenn
