使用事件机器生成qr代码

I'm developing API, based on EventMachine echo server. It listens requests on specific port and returns html-page with qr-code on it, which is generated depending on params from request query. The problem is that evaluating method, which packs string into qr-code takes from 8 to 11 seconds, it is unacceptable. I have no ideas why it happens, except it could be associated with event-machine.I'm developing API, based on EventMachine echo