奇怪 Mysql 变慢，但是CPU Memory IO 都是正常的

Question

show processlist;看看有无长时间进程
uptime看看机器负载如何

Answer 1

没有，load 负载都是正常的 在 1.0 下面，4个CPU

Answer 2

row/row0mysql.c  1746  
对应到下面代码的 trx->dict_operation_lock_mode = 0;/*********************************************************************//**
Unlocks the data dictionary exclusive lock. */
UNIV_INTERN
void
row_mysql_unlock_data_dictionary(
/*=============================*/
trx_t* trx) /*!< in/out: transaction */
{
ut_a(trx->dict_operation_lock_mode == RW_X_LATCH); /* Serialize data dictionary operations with dictionary mutex:
no deadlocks can occur then in these operations */ mutex_exit(&(dict_sys->mutex));
rw_lock_x_unlock(&dict_operation_lock); trx->dict_operation_lock_mode = 0;
}

Answer 3

select now()是用的本机客户端执行的吗

Answer 4

top - 15:41:07 up 23 days, 21:57,  3 users,  load average: 0.99, 0.61, 0.55
Tasks: 120 total,   1 running, 119 sleeping,   0 stopped,   0 zombie
Cpu0  : 29.3%us,  0.0%sy,  0.0%ni, 69.0%id,  1.3%wa,  0.0%hi,  0.3%si,  0.0%st
Cpu1  :  2.7%us,  0.0%sy,  0.0%ni, 97.3%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu2  : 35.3%us,  0.3%sy,  0.0%ni, 63.0%id,  1.3%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu3  : 35.5%us,  0.3%sy,  0.0%ni, 63.9%id,  0.3%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:  20301608k total, 15821740k used,  4479868k free,    66508k buffers
Swap:  2097144k total,    82096k used,  2015048k free,   242436k cached