How to measure mmap I/O latency?

I have an application which appears to be slowing/blocking at the same time there's a lot of disk I/O going on, so I suspect it's I/O operations within the application which are blocking. I can't imagine what else the problem might be, but I would like to confirm it. The problem is that the application largely uses mmap'd files for I/O, and thus they don't show up with strace. I know blocking I/O operations from mmap'd memory is going to be a page fault. But is there a way to measure the amount of time thread execution was suspended due to page faults?