"You can't disable disk caching. The only reason anyone ever wants to disable disk caching is because they think it takes memory away from their applications, which it doesn't! You can't disable disk caching. The only reason anyone ever wants to disable disk caching is because they think it takes memory away from their applications, which it doesn't! "http://www.linuxatemyram.com/
А подкорректировать лимит по памяти я могу? Надо смотреть в Documentation/vfs?