系統版本是5.2，把安裝memcached的方法記錄下先：
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
#安裝libevent
tar -zxvf libevent-1.4.10-stable.tar.gz
cd libevent-1.4.10-stable
./configure
make
make install
#安裝memcached
cd ..
tar -zxvf memcached-1.2.8.tar.gz
cd memcached-1.2.8
./configure
make
make install
#如果是64位系統，還需要把libevent的文件復制到/wp-content/lib64/下，用來解決error while loading shared libraries的問題
cp -R /wp-content/local/lib/libevent* /wp-content/lib64/
好了，開始安裝php的擴展，惡夢開始了，本以為直接用yum來安裝php-devel.x86_64和php-pecl-memcache.x86_64這兩個擴展就可以了，可裝了后 phpinfo()里根本找不到memcache擴展，把已經裝的這兩個擴展remove重來，還是不行，goooooooooooooogle，找到了一篇文章《PHP Pecl Memcached module installation problems》，有救嘍，先remove掉php-pecl-memcache.x86_64，然后執行了
pecl install memcache
順利安裝上了，打開/etc/php.d/看了下，沒有memcache.ini，好吧，手動到/etc/php.ini加上了 extension=memcache.so，好了，重啟httpd，刷新 phpinfo() ，竟然還沒有，我郁悶了。。
回頭想想，我好像漏了一個地方沒有檢查，馬上打開 /wp-content/lib64/php/modules/ 查看，果然沒有memcache.so，會在哪呢？ find -name之，原來躲在 /wp-content/local/lib/php/extensions/no-debug-non-zts-20060613/ 下，復制到 /wp-content/lib64/php/modules/ 再試，久違的 memcache擴展出現了。 T T
Memcached參數說明：
- -d選項是啟動一個守護進程
- -m分配給Memcache使用的內存數量，單位是MB
- -u運行Memcache的用戶
- -l監聽的服務器IP地址
- -p設置Memcache監聽的端口,最好是1024以上的端口
- -c最大運行的并發連接數，默認是1024，按照你服務器的負載量來設定
- -P設置保存Memcache的pid文件
啟動：
memcached -d -u root -m 128 -c 8192
查看狀態：
watch “echo stats | nc 127.0.0.1 11211″
狀態說明：
- uptime：memcached運行的秒數
- cmd_get：查詢緩存的次數。這兩個數據相除一下就能得到平均每秒請求緩存的次數
- cmd_set：設置key=>value的次數
- get_hits：緩存命中的次數。緩存命中率 = get_hits/cmd_get * 100%
- scurr_items：現在在緩存中的鍵值對個數
相關網址：
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]
