When action function calls apex controller method to upload a file it shows an error and abort the execution.

It shows a message when i start execution of action function.

Request entity is too large
You have an request that is too large (posted form is too big, URL is too long, etc)
__MISSING LABEL__ PropertyFile - val JettyIllegalRequest_reason not found in section Exception: Form too large 26976850>25000000