InnoDB error: mmap(275513344 bytes) failed; errno 12. How to solve?

Question

MySQL

Good day.
Please advise with a solution to the problem.
What we have, VPS: KVM SSD Ferrum (1 CPU/1 GB RAM/20 GB SSD) ; Centos 7(php-fpm + ngix+ mysql)
Only one WP site is running on the server
Database is constantly crashing

mysql logs

180808 03:02:00 mysqld_safe mysqld from pid file /var/run/mariadb/mariadb.pid ended
180808 08:58:56 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
180808  8:58:56 [Note] /usr/libexec/mysqld (mysqld 5.5.56-MariaDB) starting as process 1124 ...
180808  8:58:56 InnoDB: The InnoDB memory heap is disabled
180808  8:58:56 InnoDB: Mutexes and rw_locks use GCC atomic builtins
180808  8:58:56 InnoDB: Compressed tables use zlib 1.2.7
180808  8:58:56 InnoDB: Using Linux native AIO
180808  8:58:56 InnoDB: Initializing buffer pool, size = 256.0M
180808  8:58:56 InnoDB: Completed initialization of buffer pool
180808  8:58:56 InnoDB: highest supported file format is Barracuda.
InnoDB: The log sequence number in ibdata files does not match
InnoDB: the log sequence number in the ib_logfiles!
InnoDB: Restoring possible half-written data pages from the doublewrite buffer...
180808  8:58:56  InnoDB: Waiting for the background threads to start
180808  8:58:57 Percona XtraDB (http://www.percona.com) 5.5.52-MariaDB-38.3 started; log sequence number 715645817
180808  8:58:57 [Note] Plugin 'FEEDBACK' is disabled.
180808  8:58:57 [Note] Server socket created on IP: '127.0.0.1'.
180808  8:58:57 [Note] Event Scheduler: Loaded 0 events
180808  8:58:57 [Note] /usr/libexec/mysqld: ready for connections.
Version: '5.5.56-MariaDB'  socket: '/var/lib/mysql/mysql.sock'  port: 3306  MariaDB Server
180810 03:00:58 mysqld_safe Number of processes running now: 0
180810 03:00:58 mysqld_safe mysqld restarted
180810  3:00:58 [Note] /usr/libexec/mysqld (mysqld 5.5.56-MariaDB) starting as process 21067 ...
180810  3:00:58 InnoDB: The InnoDB memory heap is disabled
180810  3:00:58 InnoDB: Mutexes and rw_locks use GCC atomic builtins
180810  3:00:58 InnoDB: Compressed tables use zlib 1.2.7
180810  3:00:58 InnoDB: Using Linux native AIO
180810  3:00:59 InnoDB: Initializing buffer pool, size = 256.0M
InnoDB: mmap(275513344 bytes) failed; errno 12
180810  3:00:59 InnoDB: Completed initialization of buffer pool
180810  3:00:59 InnoDB: Fatal error: cannot allocate memory for the buffer pool
180810  3:00:59 [ERROR] Plugin 'InnoDB' init function returned error.
180810  3:00:59 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
180810  3:00:59 [Note] Plugin 'FEEDBACK' is disabled.
180810  3:00:59 [ERROR] Unknown/unsupported storage engine: InnoDB
180810  3:00:59 [ERROR] Aborting

180810  3:00:59 [Note] /usr/libexec/mysqld: Shutdown complete

180810 03:00:59 mysqld_safe mysqld from pid file /var/run/mariadb/mariadb.pid ended
180810 11:38:28 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
180810 11:38:28 [Note] /usr/libexec/mysqld (mysqld 5.5.56-MariaDB) starting as process 1124 ...
180810 11:38:28 InnoDB: The InnoDB memory heap is disabled
180810 11:38:28 InnoDB: Mutexes and rw_locks use GCC atomic builtins
180810 11:38:28 InnoDB: Compressed tables use zlib 1.2.7
180810 11:38:28 InnoDB: Using Linux native AIO
180810 11:38:28 InnoDB: Initializing buffer pool, size = 256.0M
180810 11:38:28 InnoDB: Completed initialization of buffer pool
180810 11:38:28 InnoDB: highest supported file format is Barracuda.
InnoDB: The log sequence number in ibdata files does not match
InnoDB: the log sequence number in the ib_logfiles!
InnoDB: Restoring possible half-written data pages from the doublewrite buffer...
180810 11:38:28  InnoDB: Waiting for the background threads to start
180810 11:38:29 Percona XtraDB (http://www.percona.com) 5.5.52-MariaDB-38.3 started; log sequence number 721208202
180810 11:38:29 [Note] Plugin 'FEEDBACK' is disabled.
180810 11:38:29 [Note] Server socket created on IP: '127.0.0.1'.
180810 11:38:29 [Note] Event Scheduler: Loaded 0 events
180810 11:38:29 [Note] /usr/libexec/mysqld: ready for connections.
Version: '5.5.56-MariaDB'  socket: '/var/lib/mysql/mysql.sock'  port: 3306  MariaDB Server
180811 20:21:56 mysqld_safe Number of processes running now: 0
180811 20:21:56 mysqld_safe mysqld restarted
180811 20:21:56 [Note] /usr/libexec/mysqld (mysqld 5.5.56-MariaDB) starting as process 12654 ...
180811 20:21:56 InnoDB: The InnoDB memory heap is disabled
180811 20:21:56 InnoDB: Mutexes and rw_locks use GCC atomic builtins
180811 20:21:56 InnoDB: Compressed tables use zlib 1.2.7
180811 20:21:56 InnoDB: Using Linux native AIO
180811 20:21:56 InnoDB: Initializing buffer pool, size = 256.0M
InnoDB: mmap(275513344 bytes) failed; errno 12
180811 20:21:56 InnoDB: Completed initialization of buffer pool
180811 20:21:56 InnoDB: Fatal error: cannot allocate memory for the buffer pool
180811 20:21:56 [ERROR] Plugin 'InnoDB' init function returned error.
180811 20:21:56 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
180811 20:21:56 [Note] Plugin 'FEEDBACK' is disabled.
180811 20:21:56 [ERROR] Unknown/unsupported storage engine: InnoDB
180811 20:21:56 [ERROR] Aborting

180811 20:21:56 [Note] /usr/libexec/mysqld: Shutdown complete

180811 20:21:56 mysqld_safe mysqld from pid file /var/run/mariadb/mariadb.pid ended