linux – MySQL在小型网站上的高CPU使用率

我有一个托管在专用服务器上的小网站(FreeBSD 9.2,MySQL 5.6.1和php 5.5.5).
问题是,即使网站上有少量访问者,MySQL也会占用大量的cpu资源.
数据库很小(最大的表约为12k行)

我在my.conf中启用了慢查询登录,但没有记录查询.

错误日志文件不包含任何有用的信息(实际上它是空的)

这是服务器规格

中央处理器

hw.machine: amd64
hw.model: Intel(R) Xeon(R) CPU           X3330  @ 2.66GHz
hw.ncpu: 4
hw.machine_arch: amd64

HHD转移信息

Seek times:
    Full stroke:      250 iter in   1.507837 sec =    6.031 msec
    Half stroke:      250 iter in   1.461401 sec =    5.846 msec
    Quarter stroke:   500 iter in   5.829283 sec =   11.659 msec
    Short forward:    400 iter in   2.668680 sec =    6.672 msec
    Short backward:   400 iter in   3.261849 sec =    8.155 msec
    Seq outer:   2048 iter in   0.247219 sec =    0.121 msec
    Seq inner:   2048 iter in   0.246036 sec =    0.120 msec
Transfer rates:
    outside:       102400 kbytes in   1.207812 sec =    84781 kbytes/sec
    middle:        102400 kbytes in   1.342168 sec =    76294 kbytes/sec
    inside:        102400 kbytes in   1.893578 sec =    54078 kbytes/sec
I/O command overhead:
    time to read 10MB block      0.131751 sec   =    0.006 msec/sector
    time to read 20480 sectors   2.170542 sec   =    0.106 msec/sector
    calculated command overhead 

    =    0.100 msec/sector

顶部(在负载高的时刻)

Mem: 1518M Active,1396M Inact,732M Wired,50M Cache,435M Buf,239M Free
 4949 mysql          27  52    0  2236M  1434M uwait   3 180:02 66.26% mysqld

my.cnf中

[mysqld]
sql_mode=NO_ENGINE_SUBSTITUTION
skip-external-locking
max_connections=5000
max_connect_errors=1500
ft_min_word_len = 2
myisam_sort_buffer_size = 64M

# Log slow queries
slow_query_log = 1
slow_query_log_file = /var/log/slow-queries.log
long_query_time = 1
key_buffer              = 384M
max_allowed_packet      = 32M
thread_stack            = 128K
thread_cache_size       = 128
thread_concurrency      = 16

wait_timeout            = 2000
interactive_timeout     = 10000
join_buffer_size = 1M
sort_buffer_size = 2M
read_buffer_size = 1M
read_rnd_buffer_size = 2M
query_cache_size = 268435456
query_cache_type=1
query_cache_limit=1048576

我不知道出了什么问题.