我正在做一个性能testing。 当我达到100-200个并发用户时， MySQL简单地closures并重新启动，而不会在日志文件中出现任何错误。 非常非常奇怪 MySQL版本是5.6.34，在CentOS 6上运行。 这是我如何configuration它：
[mysqld] innodb_buffer_pool_size = 512M max_connections = 9000 innodb_thread_concurrency = 0 innodb_read_io_threads = 64 innodb_write_io_threads = 64 innodb_io_capacity = 5000 datadir = /data/mysql socket = /data/mysql/mysql.sock sql_mode=NO_ENGINE_SUBSTITUTION
这里是MySQL如何启动：
170212 19:06:15 mysqld_safe Number of processes running now: 0 170212 19:06:15 mysqld_safe mysqld restarted 2017-02-12 19:06:19 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details). 2017-02-12 19:06:19 0 [Note] /usr/sbin/mysqld (mysqld 5.6.34) starting as process 26911 ... 2017-02-12 19:06:19 26911 [Note] Plugin 'FEDERATED' is disabled. 2017-02-12 19:06:19 26911 [Note] InnoDB: Using atomics to ref count buffer pool pages 2017-02-12 19:06:19 26911 [Note] InnoDB: The InnoDB memory heap is disabled 2017-02-12 19:06:19 26911 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins 2017-02-12 19:06:19 26911 [Note] InnoDB: Memory barrier is not used 2017-02-12 19:06:19 26911 [Note] InnoDB: Compressed tables use zlib 1.2.3 2017-02-12 19:06:19 26911 [Note] InnoDB: Using Linux native AIO 2017-02-12 19:06:19 26911 [Note] InnoDB: Using CPU crc32 instructions 2017-02-12 19:06:19 26911 [Note] InnoDB: Initializing buffer pool, size = 512.0M 2017-02-12 19:06:19 26911 [Note] InnoDB: Completed initialization of buffer pool 2017-02-12 19:06:19 26911 [Note] InnoDB: Highest supported file format is Barracuda. 2017-02-12 19:06:19 26911 [Note] InnoDB: The log sequence numbers 310826427 and 310826427 in ibdata files do not match the log sequence number 310826447 in the ib_logfiles! 2017-02-12 19:06:19 26911 [Note] InnoDB: Database was not shutdown normally! 2017-02-12 19:06:19 26911 [Note] InnoDB: Starting crash recovery. 2017-02-12 19:06:19 26911 [Note] InnoDB: Reading tablespace information from the .ibd files... 2017-02-12 19:06:19 26911 [Note] InnoDB: Restoring possible half-written data pages 2017-02-12 19:06:19 26911 [Note] InnoDB: from the doublewrite buffer... 2017-02-12 19:06:19 26911 [Note] InnoDB: 128 rollback segment(s) are active. 2017-02-12 19:06:19 26911 [Note] InnoDB: Waiting for purge to start 2017-02-12 19:06:19 26911 [Note] InnoDB: 5.6.34 started; log sequence number 310826447 2017-02-12 19:06:19 26911 [Note] Server hostname (bind-address): '*'; port: 3306 2017-02-12 19:06:19 26911 [Note] IPv6 is available. 2017-02-12 19:06:19 26911 [Note] - '::' resolves to '::'; 2017-02-12 19:06:19 26911 [Note] Server socket created on IP: '::'. 2017-02-12 19:06:19 26911 [Note] Event Scheduler: Loaded 0 events 2017-02-12 19:06:19 26911 [Note] /usr/sbin/mysqld: ready for connections. Version: '5.6.34' socket: '/data/mysql/mysql.sock' port: 3306 MySQL Community Server (GPL)
提前致谢！
正如@shodanshok所build议的，我查看了/var/log/messages 。 我find了这个：
Feb 12 18:06:08 prosveta kernel: Out of memory: Kill process 23277 (mysqld) score 351 or sacrifice child Feb 12 18:06:08 prosveta kernel: Killed process 23277, UID 27, (mysqld) total-vm:3908768kB, anon-rss:2086896kB, file-rss:1916kB Feb 12 18:06:08 prosveta kernel: php-cgi invoked oom-killer: gfp_mask=0x280da, order=0, oom_adj=0, oom_score_adj=0 Feb 12 18:06:08 prosveta kernel: php-cgi cpuset=/ mems_allowed=0 Feb 12 18:06:08 prosveta kernel: Pid: 30182, comm: php-cgi Not tainted 2.6.32-642.11.1.el6.x86_64 #1
因此，内核已经杀死了MySQL ，但是我怎样才能避免这种情况呢？ 谢谢。
它可能正在被内核的OOM杀手所杀，而幸存的mysqld-safe重启主进程。 检查dmesg是否有趣的消息（尝试dmesg | grep -i oom ）
因此，内核已经杀死了MySQL，但是我怎样才能避免这种情况呢？
添加更多的内存。