因为有几天我的mysql服务器崩溃了，每隔几个小时就重启一次。
我检查过的东西：syslog没有给我任何提示
mysql错误日志显示：

2018-08-22T10:28:25.602376Z 0 [Note] InnoDB: page_cleaner: 1000ms intended loop took 6702ms. The settings might not be optimal. (flushed=9, during the time.)
2018-08-22T10:34:21.112124Z 0 [Note] InnoDB: page_cleaner: 1000ms intended loop took 4263ms. The settings might not be optimal. (flushed=8, during the time.)
Killed
2018-08-22T10:37:48.520909Z mysqld_safe Number of processes running now: 0
2018-08-22T10:37:48.522288Z mysqld_safe mysqld restarted
2018-08-22T10:37:48.595417Z 0 [Warning] Could not increase number of max_open_files to more than 1024 (request: 65535)
2018-08-22T10:37:48.595512Z 0 [Warning] Changed limits: max_connections: 214 (requested 500)
2018-08-22T10:37:48.595518Z 0 [Warning] Changed limits: table_open_cache: 400 (requested 10240)
2018-08-22T10:37:48.774434Z 0 [Warning] The use of InnoDB is mandatory since MySQL 5.7. The former options like '--innodb=0/1/OFF/ON' or '--skip-innodb' are ignored.
2018-08-22T10:37:48.774462Z 0 [Warning] The syntax 'avoid_temporal_upgrade' is deprecated and will be removed in a future release
2018-08-22T10:37:48.775643Z 0 [Warning] 'NO_AUTO_CREATE_USER' sql mode was not set.
2018-08-22T10:37:48.778919Z 0 [Note] /usr/sbin/mysqld (mysqld 5.7.14-8-log) starting as process 27908 ...
2018-08-22T10:37:48.798784Z 0 [Warning] You need to use --log-bin to make --binlog-format work.
2018-08-22T10:37:48.807156Z 0 [Note] InnoDB: PUNCH HOLE support available
2018-08-22T10:37:48.807174Z 0 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2018-08-22T10:37:48.807180Z 0 [Note] InnoDB: Uses event mutexes
2018-08-22T10:37:48.807184Z 0 [Note] InnoDB: GCC builtin __atomic_thread_fence() is used for memory barrier
2018-08-22T10:37:48.807189Z 0 [Note] InnoDB: Compressed tables use zlib 1.2.8
2018-08-22T10:37:48.807194Z 0 [Note] InnoDB: Using Linux native AIO
2018-08-22T10:37:48.808810Z 0 [Note] InnoDB: Number of pools: 1
2018-08-22T10:37:48.813108Z 0 [Note] InnoDB: Using CPU crc32 instructions
2018-08-22T10:37:48.815587Z 0 [Note] InnoDB: Initializing buffer pool, total size = 28G, instances = 8, chunk size = 128M
2018-08-22T10:37:49.681807Z 0 [Note] InnoDB: Completed initialization of buffer pool
2018-08-22T10:37:49.934256Z 0 [Note] InnoDB: If the mysqld execution user is authorized, page cleaner thread priority can be changed. See the man page of setpriority().
2018-08-22T10:37:49.943100Z 0 [Note] InnoDB: Recovering partial pages from the parallel doublewrite buffer at /var/lib/mysql/xb_doublewrite
2018-08-22T10:37:50.039106Z 0 [Note] InnoDB: Highest supported file format is Barracuda.
2018-08-22T10:37:50.250493Z 0 [Note] InnoDB: Log scan progressed past the checkpoint lsn 1253064250683
2018-08-22T10:37:50.569591Z 0 [Note] InnoDB: Doing recovery: scanned up to log sequence number 1253069493248

几十个'做恢复'通知后。
munin告诉我innodb池的大小可能是问题所在。日志中有很多这样的信息：

2018-08-22T10:39:10.793549Z 0 [Note] InnoDB: page_cleaner: 1000ms intended loop took 7779ms. The settings might not be optimal. (flushed=11, during the time.)

my.cnf配置设置

# INNODB #

innodb-flush-method            = O_DIRECT
innodb-log-files-in-group      = 2
innodb-log-file-size           = 1G
innodb-flush-log-at-trx-commit = 2
innodb-file-per-table          = 1
innodb-buffer-pool-size        = 28G

我有点纠结于如何解决问题。