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Date: Tue, 15 Jul 2008 16:37:00 -0700
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From: JINMEI Tatuya / =?ISO-2022-JP?B?GyRCP0BMQEMjOkgbKEI=?=
	<Jinmei_Tatuya@isc.org>
To: Bakul Shah <bakul@bitblocks.com>
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	<20080715230917.DAC3B5B46@mail.bitblocks.com>
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Cc: freebsd-net@freebsd.org, Kris Kennaway <kris@FreeBSD.org>,
	Thomas Vogt <freebsdlists@bsdunix.ch>
Subject: Re: too many open file descriptors messages since bind
	9.4.2-P1	(port dns94) 
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At Tue, 15 Jul 2008 16:09:17 -0700,
Bakul Shah <bakul@bitblocks.com> wrote:

> IIRC, when poll() returns n, you only look at the first n
> values in the pollfd array so it is a win when you expect a
> very small number of fds to be ready.  In the select case you
> have to test the bit array until you see the last ready fd.

% uname -a 
FreeBSD opt1.jinmei.org 7.0-RC1 FreeBSD 7.0-RC1 #0: Fri Jan 25 15:17:04 PST 2008     root@opt1.jinmei.org:/usr/src/sys/amd64/compile/GENERIC_NOSMP  amd64
(please ignore "RC1":-)

% cat polltest.c
(omitted here, see below)

% cc -o polltest polltest.c

% ./polltest
poll returned: 1
999th socket is ready (fd=1002)

Perhaps You're probably confused poll(2) with /dev/poll.  The latter
behaves as you described (but is not portable as poll(2)).

---
JINMEI, Tatuya
Internet Systems Consortium, Inc.

out put of polltest.c
#include <sys/types.h>
#include <sys/socket.h>

#include <netinet/in.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <poll.h>

main()
{
	int i, n;
	struct pollfd pfds[1000];
	struct sockaddr_in sin;
	socklen_t sin_len;
	char buf[16];

	memset(pfds, 0, sizeof(pfds));

	memset(&sin, 0, sizeof(sin));
	sin.sin_family = AF_INET;
	sin.sin_len = sizeof(sin);
	inet_pton(AF_INET, "127.0.0.1", &sin.sin_addr);
	for (i = 0; i < 1000; i ++) {
		if ((pfds[i].fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))
		    < 0) {
			perror("socket");
			exit(1);
		}
		if (bind(pfds[i].fd, (struct sockaddr *)&sin, sizeof(sin)) < 0) {
			perror("bind");
			exit(1);
		}
		pfds[i].events = POLLIN; 
	}

	sin_len = sizeof(sin);
	if (getsockname(pfds[999].fd, (struct sockaddr *)&sin, &sin_len) < 0) {
		perror("getsockname");
		exit(1);
	}

	if (sendto(pfds[999].fd, buf, sizeof(buf), 0, (struct sockaddr *)&sin,
		   sizeof(sin)) < 0) {
		perror("sendto");
		exit(1);
	}

	n = poll(pfds, 1000, -1);

	printf("poll returned: %d\n", n);

	for (i = 0; i < 1000; i++) {
		if ((pfds[i].revents & POLLIN) != 0) {
			printf("%dth socket is ready (fd=%d)\n", i, pfds[i].fd);
		}
	}

	exit(0);
}