关于缓存优化： 1. 直接读取数据库，68.22kb的数据耗时126ms

GET /style/images/number9.png 304 0ms

----read from redis

----read from mysql

----get result

---- POST /ajax/get_category_good_list/ 200 126ms - 68.22kb

---- POST /ajax/start/ 200 4ms - 194b

---- GET /single/category/ 200 6ms - 11.38kb

  1. 从redis缓存里面读取数据，68.22kb耗时9ms

----read from redis

----return result from redis

----get result