最近安装好了MySQL之后，在启动MySQL服务时无法正常启动MySQL。提示没有更新/var/lib/mfailedZDB.pid并退出。该MySQL与Oracle位于同一主机。有些内核参数进行过调整应该也是使用与MySQL。下面是该问题的具体描述。
1、故障现象
SZDB:/usr/src/mysql_src # /etc/init.d/mysql start
Starting MySQL...The server quit without updating PID file (/var/lib/mfailedZDB.pid).
SZDB:~ # cat /etc/issue #故障环境
Welcome to SUSE Linux Enterprise Server 10 SP3 (x86_64) - Kernel \r (\l).
2、故障分析
#查看err日志信息
SZDB:/var/lib/mysql # more SZDB.err
140505 16:05:59 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
140505 16:05:59 [Note] Plugin 'FEDERATED' is disabled.
140505 16:05:59 InnoDB: The InnoDB memory heap is disabled
140505 16:05:59 InnoDB: Mutexes and rw_locks use GCC atomic builtins
140505 16:05:59 InnoDB: Compressed tables use zlib 1.2.3
140505 16:05:59 InnoDB: Using Linux native AIO
140505 16:05:59 InnoDB: Warning: io_setup() failed with EAGAIN. Will make 5 attempts before giving up.
InnoDB: Warning: io_setup() attempt 1 failed.
InnoDB: Warning: io_setup() attempt 2 failed.
InnoDB: Warning: io_setup() attempt 3 failed.
InnoDB: Warning: io_setup() attempt 4 failed.
InnoDB: Warning: io_setup() attempt 5 failed.
140505 16:06:02 InnoDB: Error: io_setup() failed with EAGAIN after 5 attempts.
InnoDB: You can disable Linux Native AIO by setting innodb_use_native_aio = 0 in my.cnf
140505 16:06:02 InnoDB: Fatal error: cannot initialize AIO sub-system
140505 16:06:02 [ERROR] Plugin 'InnoDB' init function returned error.
140505 16:06:02 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
140505 16:06:02 [ERROR] Unknown/unsupported storage engine: InnoDB
140505 16:06:02 [ERROR] Aborting
140505 16:06:02 [Note] /usr/sbin/mysqld: Shutdown complete
140505 16:06:02 mysqld_safe mysqld from pid file /var/lib/mysql/SZDB.pid ended
#从上面的错误日志中可以看到，关键的一个信息io_setup() failed with EAGAIN
#io_setup()锁定失败
3、故障解决
错误代码EAGAIN表明超出了可用event限制的最大值(见第4点中的描述)
SZDB:~ # cat /proc/sys/fs/aio-max-nr
65536 #64k个
SZDB:~ # vi /etc/sysctl.conf
fs.aio-max-nr=262144 #调整为256k个
SZDB:~ # sysctl -p
# Author : Leshami
# Blog : http://blog.csdn.net/leshami
SZDB:~ # /etc/init.d/mysql start #调整后启动成功
Starting MySQL... done
4、关于fs.aio-max-nr
该参数指同时可以拥有的的异步IO请求数目
aio-nr & aio-max-nr:
aio-nr is the running total of the number of events specified on the
io_setup system call for all currently active aio contexts. If aio-nr
reaches aio-max-nr then io_setup will fail with EAGAIN. Note that
raising aio-max-nr does not result in the pre-allocation or re-sizing
of any kernel data structures.
NAME
io_setup - Create an asynchronous I/O context
SYNOPSIS
#include <libaio.h>
Tag Description
----------- ------------------------------------
int io_setup (int maxevents, io_context_t *ctxp);
DESCRIPTION:
io_setup() creates an asynchronous I/O context capable of receiving at least maxevents.#创建一个接收异步i/o的上下文环境
ctxp must not point to an AIO context that already exists, and must be initialized to 0 prior to the call.
On successful creation of the AIO context, *ctxp is filled in with the resulting handle.
RETURN VALUE：
io_setup() returns 0 on success; otherwise, one of the errors listed in the "Errors" section is returned.
ERRORS：
Tag Description
------ ----------------------------------------------
EINVAL ctxp is not initialized,or the specified maxevents exceeds internal limits. maxevents should be greater than 0.
EFAULT An invalid pointer is passed for ctxp.
ENOMEM Insufficient kernel resources are available.
EAGAIN The specified maxevents exceeds the user’s limit of available events.#此案例中返回的时超出了可用event限制的最大值
ENOSYS io_setup() is not implemented on this architecture.
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