Question

Any recommendations out there for Windows application tuning resources (books web sites etc.)?

I have a C++ console application that needs to feed a hardware device with a considerable amount of data at a fairly high rate. (buffer is 32K in size and gets consumed at ~800k bytes per second)

It will stream data without under runs, except when I perform file IO like opening a folder etc… (It seems to be marginally meeting its timing requirements).

Anyway.. a good book or resource to brush up on realtime performance with windows would be helpful.

Thanks!

Answer 1

The best you can hope for on commodity Windows is “usually meets timing requirements”. If the system is running any processes other than your target app, it will occasionally miss deadlines due scheduling inconsistencies. However, if your app/hardware can handle the rare but occasional misses, there are a few things you can do to reduce the number of misses.

1. Set your process’s priority to REALTIME_PRIORITY_CLASS
2. Change the scheduler’s granularity to 1ms resolution via the timeBeginPeriod() function (part of the Windows Multimedia libraries)
3. Avoid as many system calls in your main loop as possible (this includes allocating memory). Each syscall is an opportunity for the OS to put the process to sleep and, consequently, is an opportunity for the non-deterministic scheduler to miss the next deadline

If this doesn’t get the job done for you, you might consider trying a Linux distribution with realtime kernel patches applied. I’ve found those to provide near-perfect timing (within 10s of microseconds accuracy over the course of several hours). That said, nothing short of a true-realtime OS will actually give you perfection but the realtime-linux distros are much closer than commodity Windows.