系统版本是5.2，把安装memcached的方法记录下先：
cd ~/memcached
wget -c http://www.monkey.org/~provos/libevent-1.4.10-stable.tar.gz
wget -c http://memcached.googlecode.com/files/memcached-1.2.8.tar.gz
#安装libevent
tar -zxvf libevent-1.4.10-stable.tar.gz
cd libevent-1.4.10-stable
./configure
make
make install
#安装memcached
cd ..
tar -zxvf memcached-1.2.8.tar.gz
cd memcached-1.2.8
./configure
make
make install
#如果是64位系统，还需要把libevent的文件复制到/wp-content/lib64/下，用来解决error while loading shared libraries的问题
cp -R /wp-content/local/lib/libevent* /wp-content/lib64/
好了，开始安装php的扩展，恶梦开始了，本以为直接用yum来安装php-devel.x86_64和php-pecl-memcache.x86_64这两个扩展就可以了，可装了后 phpinfo()里根本找不到memcache扩展，把已经装的这两个扩展remove重来，还是不行，goooooooooooooogle，找到了一篇文章《PHP Pecl Memcached module installation problems》，有救喽，先remove掉php-pecl-memcache.x86_64，然后执行了
pecl install memcache
顺利安装上了，打开/etc/php.d/看了下，没有memcache.ini，好吧，手动到/etc/php.ini加上了 extension=memcache.so，好了，重启httpd，刷新 phpinfo() ，竟然还没有，我郁闷了。。
回头想想，我好像漏了一个地方没有检查，马上打开 /wp-content/lib64/php/modules/ 查看，果然没有memcache.so，会在哪呢？ find -name之，原来躲在 /wp-content/local/lib/php/extensions/no-debug-non-zts-20060613/ 下，复制到 /wp-content/lib64/php/modules/ 再试，久违的 memcache扩展出现了。 T T
Memcached参数说明：
-d选项是启动一个守护进程 -m分配给Memcache使用的内存数量，单位是MB -u运行Memcache的用户 -l监听的服务器IP地址 -p设置Memcache监听的端口,最好是1024以上的端口 -c最大运行的并发连接数，默认是1024，按照你服务器的负载量来设定 -P设置保存Memcache的pid文件
启动：
memcached -d -u root -m 128 -c 8192
查看状态：
watch “echo stats | nc 127.0.0.1 11211″
状态说明：
uptime：memcached运行的秒数 cmd_get：查询缓存的次数。这两个数据相除一下就能得到平均每秒请求缓存的次数 cmd_set：设置key=>value的次数 get_hits：缓存命中的次数。缓存命中率 = get_hits/cmd_get * 100% scurr_items：现在在缓存中的键值对个数
相关网址：
Libevent：http://www.monkey.org/~provos/libevent/
Memcached：http://danga.com/memcached/
PHP Memcached Extension：http://pecl.php.net/package/memcache
[shell]
[root@~]# pecl install memcache
downloading memcache-2.2.6.tgz ...
Starting to download memcache-2.2.6.tgz (35,957 bytes)
..........done: 35,957 bytes
11 source files, building
WARNING: php_bin /opt/php/bin/php appears to have a suffix /bin/php, but config variable php_suffix does not match
running: phpize
Configuring for:
PHP Api Version: 20090626
Zend Module Api No: 20090626
Zend Extension Api No: 220090626
Enable memcache session handler support? [yes] : n
[/shell]
[shell]
running: make INSTALL_ROOT="/var/tmp/pear-build-root/install-memcache-2.2.6" install
Installing shared extensions: /var/tmp/pear-build-root/install-memcache-2.2.6/opt/php/lib/php/extensions/no-debug-non-zts-20090626/
running: find "/var/tmp/pear-build-root/install-memcache-2.2.6" | xargs ls -dils
11370548 4 drwxr-xr-x 3 root root 4096 Jan 6 15:55 /var/tmp/pear-build-root/install-memcache-2.2.6
11370602 4 drwxr-xr-x 3 root root 4096 Jan 6 15:55 /var/tmp/pear-build-root/install-memcache-2.2.6/opt
11370603 4 drwxr-xr-x 3 root root 4096 Jan 6 15:55 /var/tmp/pear-build-root/install-memcache-2.2.6/opt/php
11370604 4 drwxr-xr-x 3 root root 4096 Jan 6 15:55 /var/tmp/pear-build-root/install-memcache-2.2.6/opt/php/lib
11370605 4 drwxr-xr-x 3 root root 4096 Jan 6 15:55 /var/tmp/pear-build-root/install-memcache-2.2.6/opt/php/lib/php
11370606 4 drwxr-xr-x 3 root root 4096 Jan 6 15:55 /var/tmp/pear-build-root/install-memcache-2.2.6/opt/php/lib/php/extensions
11370607 4 drwxr-xr-x 2 root root 4096 Jan 6 15:55 /var/tmp/pear-build-root/install-memcache-2.2.6/opt/php/lib/php/extensions/no-debug-non-zts-20090626
11370601 236 -rwxr-xr-x 1 root root 235639 Jan 6 15:55 /var/tmp/pear-build-root/install-memcache-2.2.6/opt/php/lib/php/extensions/no-debug-non-zts-20090626/memcache.so
Build process completed successfully
Installing '/opt/php/lib/php/extensions/no-debug-non-zts-20090626/memcache.so'
install ok: channel://pecl.php.net/memcache-2.2.6
configuration option "php_ini" is not set to php.ini location
You should add "extension=memcache.so" to php.ini
[/shell]
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