windtear 追求完美

http://windtear.net/archives/2005/08/02/000733.html

epoll poll select - squid compile options

依次优先 有epoll用epoll 没有就用poll
(epoll比较好些 需要打squid补丁和操作系统epoll库支持)
http://devel.squid-cache.org/cgi-bin/diff2/epoll-2_5.patch?s2_5
http://www.xmailserver.org/linux-patches/epoll-lib-0.11.tar.gz

POLL(2)                    Linux Programmer's Manual                   POLL(2)

NAME
       poll - wait for some event on a file descriptor

SYNOPSIS
       #include <sys/poll.h>

       int poll(struct pollfd *ufds, unsigned int nfds, int timeout);

fds是一个结构指针
               struct pollfd {
                       int fd;           /* file descriptor */
                       short events;     /* requested events */
                       short revents;    /* returned events */
               };
指向一组需要检测的文件描述符
nfds是这个集合的大小

大小比较大的时候 就出现了瓶颈  造成了极大的资源浪费

Redhat RPM默认是 --enable-poll 的
Summary: The Squid proxy caching server.
Name: squid
Version: 2.4.STABLE6
Release: 6.7.3
Serial: 7

%configure \
   --exec_prefix=/usr --bindir=/usr/sbin --libexecdir=/usr/lib/squid \
   --localstatedir=/var --sysconfdir=/etc/squid \
   --enable-poll --enable-snmp --enable-removal-policies="heap,lru" \
   --enable-storeio="aufs,coss,diskd,ufs" \
   --enable-delay-pools --enable-linux-netfilter \
   --with-pthreads \
   --enable-auth-modules="LDAP,NCSA,PAM,SMB,MSNT"  # --enable-icmp

SELECT(2)                  Linux Programmer's Manual                 SELECT(2)

NAME
       select,  pselect,  FD_CLR,  FD_ISSET, FD_SET, FD_ZERO - synchronous I/O
       multiplexing

SYNOPSIS
       /* According to POSIX 1003.1-2001 */
       #include <sys/select.h>

       /* According to earlier standards */
       #include <sys/time.h>
       #include <sys/types.h>
       #include <unistd.h>

       int select(int n, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
       struct timeval *timeout);

       int   pselect(int   n,   fd_set   *readfds,  fd_set  *writefds,  fd_set
       *exceptfds, const struct timespec *timeout, const sigset_t *sigmask);

       FD_CLR(int fd, fd_set *set);
       FD_ISSET(int fd, fd_set *set);
       FD_SET(int fd, fd_set *set);
       FD_ZERO(fd_set *set);