nginx location中可能涉及的匹配规则有
= 精确匹配
^~ 普通字符匹配,区分大小写
~ 正则匹配,区分大小写
/xxx/yyy.zzz 最长匹配
/
本文所用的nginx版本是 
[root@node1 nginx]# nginx -v 
nginx version: nginx/1.4.3
实验机器ip为192.168.151.70,浏览器为IE8,不保存cookies。依次对上面的五个匹配规则两两进行对比实验。
1.  =  对比 ^~
        location ^~  /p_w_picpaths {
                rewrite ^/p_w_picpaths http://www.baidu.com permanent;
        }

        location  = /p_w_picpaths {
                rewrite /p_w_picpaths http://www.sina.com.cn permanent;
        }
结果
[root@agent3 tmp]# wget http://192.168.151.70/p_w_picpaths
--12:05:53--  http://192.168.151.70/p_w_picpaths
Connecting to 192.168.151.70:80... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: http://www.sina.com.cn [following]
--12:05:53--  http://www.sina.com.cn/
Resolving www.sina.com.cn... 61.172.201.194, 61.172.201.195
Connecting to www.sina.com.cn|61.172.201.194|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 690283 (674K) [text/html]
Saving to: `index.html'

100%[========================================================================>] 690,283     --.-K/s   in 0.08s  

12:05:54 (8.45 MB/s) - `index.html' saved [690283/690283]
=优先级大于^~

2. = 对比 ~
        location ~  /p_w_picpaths {
                rewrite ^/p_w_picpaths http://www.baidu.com permanent;
        }

        location  = /p_w_picpaths {
                rewrite /p_w_picpaths http://www.sina.com.cn permanent;
        }
结果
[root@agent3 tmp]# wget http://192.168.151.70/p_w_picpaths
--12:05:53--  http://192.168.151.70/p_w_picpaths
Connecting to 192.168.151.70:80... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: http://www.sina.com.cn [following]
--12:05:53--  http://www.sina.com.cn/
Resolving www.sina.com.cn... 61.172.201.194, 61.172.201.195
Connecting to www.sina.com.cn|61.172.201.194|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 690283 (674K) [text/html]
Saving to: `index.html'

100%[========================================================================>] 690,283     --.-K/s   in 0.08s  

12:05:54 (8.45 MB/s) - `index.html' saved [690283/690283]
=优先级大于~

3. = 对比 /xxx/yyy.zzz
        location   /p_w_picpaths/p_w_picpaths.jsp {
                rewrite ^/p_w_picpaths http://www.baidu.com permanent;
        }

        location  = /p_w_picpaths {
                rewrite /p_w_picpaths http://www.sina.com.cn permanent;
        }
结果:
[root@agent3 tmp]# wget http://192.168.151.70/p_w_picpaths/p_w_picpaths.jsp
--12:10:58--  http://192.168.151.70/p_w_picpaths/p_w_picpaths.jsp
Connecting to 192.168.151.70:80... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: http://www.sina.com.cn [following]
--12:10:58--  http://www.sina.com.cn/
Resolving www.sina.com.cn... 61.172.201.194, 61.172.201.195
Connecting to www.sina.com.cn|61.172.201.194|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 690375 (674K) [text/html]
Saving to: `index.html.1'

100%[========================================================================>] 690,375     --.-K/s   in 0.08s  

12:10:58 (8.55 MB/s) - `index.html.1' saved [690375/690375]
=优先级大于/xxx/yyy.zzz

4. = 对比 /
          location   / {
                rewrite ^/(.*)$ http://www.baidu.com permanent;
        }

        location   = / {
                rewrite ^/(.*)$ http://www.sina.com.cn permanent;
        }
结果
[root@agent3 tmp]# wget http://192.168.151.70
--12:31:09--  http://192.168.151.70/
Connecting to 192.168.151.70:80... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: http://www.sina.com.cn [following]
--12:31:09--  http://www.sina.com.cn/
Resolving www.sina.com.cn... 61.172.201.195, 61.172.201.194
Connecting to www.sina.com.cn|61.172.201.195|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 690538 (674K) [text/html]
Saving to: `index.html.6'

100%[========================================================================>] 690,538     1.93M/s   in 0.3s   

12:31:09 (1.93 MB/s) - `index.html.6' saved [690538/690538]
=优先级大于 /

5 ^~ 对比 ~
        location  ~ /p_w_picpaths {
                rewrite /p_w_picpaths http://www.baidu.com permanent;
        }

        location  ^~ /p_w_picpaths {
                rewrite /p_w_picpaths http://www.sina.com.cn permanent;
        }
结果
[root@agent3 tmp]# wget http://192.168.151.70/p_w_picpaths
--12:05:53--  http://192.168.151.70/p_w_picpaths
Connecting to 192.168.151.70:80... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: http://www.sina.com.cn [following]
--12:05:53--  http://www.sina.com.cn/
Resolving www.sina.com.cn... 61.172.201.194, 61.172.201.195
Connecting to www.sina.com.cn|61.172.201.194|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 690283 (674K) [text/html]
Saving to: `index.html'

100%[========================================================================>] 690,283     --.-K/s   in 0.08s  

12:05:54 (8.45 MB/s) - `index.html' saved [690283/690283]
^~优先级大于~
6. ^~ 对比 /xxx/yyy.zz
        location   /p_w_picpaths/p_w_picpaths.jsp {
                rewrite ^/(.*)$ http://www.baidu.com permanent;
        }

        location  ^~ /p_w_picpaths {
                rewrite ^/(.*)$ http://www.sina.com.cn permanent;
        }
结果
[root@agent3 tmp]# wget http://192.168.151.70/p_w_picpaths/p_w_picpaths.jsp
--12:10:58--  http://192.168.151.70/p_w_picpaths/p_w_picpaths.jsp
Connecting to 192.168.151.70:80... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: http://www.sina.com.cn [following]
--12:10:58--  http://www.sina.com.cn/
Resolving www.sina.com.cn... 61.172.201.194, 61.172.201.195
Connecting to www.sina.com.cn|61.172.201.194|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 690375 (674K) [text/html]
Saving to: `index.html.1'

100%[========================================================================>] 690,375     --.-K/s   in 0.08s  
^~优先级大于/xxx/yyy.zzz
12:10:58 (8.55 MB/s) - `index.html.1' saved [690375/690375]

7.  ~ 对比 /xxx/yyy.zzz
        location   /p_w_picpaths/p_w_picpaths.jsp {
                rewrite ^/(.*)$ http://www.baidu.com permanent;
        }

        location  ~ /p_w_picpaths {
                rewrite ^/(.*)$ http://www.sina.com.cn permanent;
        }
结果:
[root@agent3 tmp]# wget http://192.168.151.70/p_w_picpaths/p_w_picpaths.jsp
--12:19:17--  http://192.168.151.70/p_w_picpaths/p_w_picpaths.jsp
Connecting to 192.168.151.70:80... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: http://www.sina.com.cn [following]
--12:19:17--  http://www.sina.com.cn/
Resolving www.sina.com.cn... 61.172.201.195, 61.172.201.194
Connecting to www.sina.com.cn|61.172.201.195|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 690441 (674K) [text/html]
Saving to: `index.html.2'

100%[========================================================================>] 690,441     --.-K/s   in 0.07s  

12:19:17 (9.12 MB/s) - `index.html.2' saved [690441/690441]
~优先级大于/xxx/yyy.zzz

8. ~ 对比 /
        location   / {
                rewrite ^/(.*)$ http://www.baidu.com permanent;
        }

        location  ~ / {
                rewrite ^/(.*)$ http://www.sina.com.cn permanent;
        }
结果
[root@agent3 tmp]# wget http://192.168.151.70
--12:26:26--  http://192.168.151.70/
Connecting to 192.168.151.70:80... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: http://www.sina.com.cn [following]
--12:26:26--  http://www.sina.com.cn/
Resolving www.sina.com.cn... 61.172.201.194, 61.172.201.195
Connecting to www.sina.com.cn|61.172.201.194|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 690516 (674K) [text/html]
Saving to: `index.html.5'

100%[========================================================================>] 690,516     2.23M/s   in 0.3s   

12:26:27 (2.23 MB/s) - `index.html.5' saved [690516/690516]
~优先级大于/

9.  /xxx/yyy.zzz 对比 /
很明显,/xxx/yyy.zzz优先级大于/

总上所述location规则优先级顺序为
= > ^~ > ~ > /xxx/yyy.zzz > /