InnoDB: mmap(137363456 bytes) failed; errno 12

* Error displaying the error page application instantiation error

* Error happens while site is running and mysql database  crashes . On reboot everything start working well again.

  Error logs

140410 9:16:44 [ERROR] Native table 'performance_schema'.'file_instances' has the wrong structure 140410
9:16:44 [Note] Event Scheduler: Loaded 0 events 140410 9:16:44 [Note] /usr/sbin/mysqld: ready for connections.
Version: '5.5.29-0ubuntu0.12.04.2' socket: '/var/run/mysqld/mysqld.sock' port: 3306 (Ubuntu) 140410 21:26:53 [Note] Plugin 'FEDERATED' is disabled.
140410 21:26:53 InnoDB: The InnoDB memory heap is disabled
140410 21:26:53 InnoDB: Mutexes and rw_locks use GCC atomic builtins 140410 21:26:53 InnoDB: Compressed tables use zlib 1.2.3.4
140410 21:26:53 InnoDB: Initializing buffer pool, size = 128.0M InnoDB: mmap(137363456 bytes) failed; errno 12
 140410 21:26:53 InnoDB: Completed initialization of buffer pool
140410 21:26:53 InnoDB: Fatal error: cannot allocate memory for the buffer pool
140410 21:26:53 [ERROR] Plugin 'InnoDB' init function returned error.
140410 21:26:53 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
140410 21:26:53 [ERROR] Unknown/unsupported storage engine: InnoDB 140410 21:26:53 [ERROR] Aborting
140410 21:27:08 [Note] Plugin 'FEDERATED' is disabled.
140410 21:27:08 InnoDB: The InnoDB memory heap is disabled
140410 21:27:08 InnoDB: Mutexes and rw_locks use GCC atomic builtins 140410 21:27:08 InnoDB: Compressed tables use zlib 1.2.3.4
140410 21:27:09 InnoDB: Initializing buffer pool, size = 128.0M InnoDB: mmap(137363456 bytes) failed; errno 12
140410 21:27:09 InnoDB: Completed initialization of buffer pool
140410 21:27:09 InnoDB: Fatal error: cannot allocate memory for the buffer pool
140410 21:27:09 [ERROR] Plugin 'InnoDB' init function returned error.
140410 21:27:09 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
140410 21:27:09 [ERROR] Unknown/unsupported storage engine: InnoDB 140410 21:27:09 [ERROR] Aborting 140410 21:27:09 [Note] /usr/sbin/mysqld: Shutdown complete
140410 21:27:10 [Note] Plugin 'FEDERATED' is disabled.
140410 21:27:11 InnoDB: The InnoDB memory heap is disabled
140410 21:27:11 InnoDB: Mutexes and rw_locks use GCC atomic builtins 140410 21:27:11 InnoDB: Compressed tables use zlib 1.2.3.4
140410 21:27:11 InnoDB: Initializing buffer pool, size = 128.0M
InnoDB: mmap(137363456 bytes) failed; errno 12
140410 21:27:11 InnoDB: Completed initialization of buffer pool
140410 21:27:11 InnoDB: Fatal error: cannot allocate memory for the buffer pool
140410 21:27:11 [ERROR] Plugin 'InnoDB' init function returned error.
140410 21:27:11 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
140410 21:27:11 [ERROR] Unknown/unsupported storage engine: InnoDB 140410 21:27:11 [ERROR] Aborting 

This error might occur in InnoDB in two situation :

1. When InnoDB unable to allocate memory as specified in innodb_buffer_pool_size variable

And then reboot the system. If your problem is not solved by these steps , then look for you swap file.

2. Swap file not present .If swap file is not present you can create it by