fil_init 主要是初始化文件打开指针哈希表，所有打开的文件全记录在 fil_system 之中，构造按名字查找的哈希表 
 
buf_pool_init 内存缓冲池的初始化，对应 buf_pool_ptr 数组之中，还初始化了 adaptive hash index 的内存
 
log_init 初始化log缓冲区，默认大小为 512*16k， 每个log页面大小为 #define OS_FILE_LOG_BLOCK_SIZE  512  日志文件在创建过程中也是指定不用系统缓存
  www.2cto.com  
 lock_sys_create 初始化系统锁，就是建了一个HASH表，lock_sys
 
 recv_recovery_from_checkpoint_start 开始执行恢复
 
dict_boot 初始化表结构的缓存，dict_sys，建两个hash表，可以根据表名和表ID查找；初始化系统表，就四个 SYS_TABLES SYS_COLUMNS SYS_INDEXES SYS_FIELDS ；初始化 insert buffer，每一个表空间对应一个；读入上面四个系统表中的内容
 
trx_sys_init_at_db_start 初初化事务结构体 trx_sys ； Creates the global purge system control structure and inits the history 
 
dict_create_or_check_foreign_constraint_tables 创建另外两张系统表 SYS_FOREIGN SYS_FOREIGN_COLS  www.2cto.com  
 
启动的线程，
 
IO部分共10个，可通过参数配置
 
1个 insert buffer thread
 
1个 log thread
 
4个 aio read thread
 
4个 aio write thread
 
1个 lock timeout thread      A thread which wakes up threads whose lock wait may have lasted too long
 
1个 error monitor thread    A thread which prints warnings about semaphore waits which have lasted too long
 
1个 monitor thread           A thread which prints the info output by various InnoDB monitors
 
1个 master thread           The master thread controlling the server
 
1个 thread handle shutdown
 
1个 handle connections socket 专门用来处理连理的
 
1个 trx_rollback_or_clean_all_recovered Rollback the uncommitted transactions which have no user   session  www.2cto.com  
 
 
 
struct st__plugin *mysql_optional_plugins[]=
{
   builtin_innobase_plugin, builtin_perfschema_plugin, builtin_partition_plugin, 0
};
 
struct st_mysql_plugin *mysql_mandatory_plugins[]=
{
  builtin_binlog_plugin, builtin_mysql_password_plugin,  builtin_csv_plugin, builtin_heap_plugin, builtin_myisam_plugin, builtin_myisammrg_plugin, 0
};
初始化的 binlog memory myisam innodb pefformance_schema partition