I would like to display a list of processes (Windows, C++) and how much they are reading and writing from the disk in KB/sec.
The Resource Monitor of Windows 7 has the ability so I should be able to do the same.
However I have unable to find a relevant API-call or find anything in the perfmon counters. Could anyone point me in the direction?
You can call GetProcessIoCounters to get overall disk I/O data per process - you'll need to keep track of deltas and converting to time-based rate yourself.
This API will tell you total number of I/O operations as well as total bytes.
WMI can do it, as long as you periodically snapshot it to get differential stats for some "recent" slice of time. This post presents a peculiarly mixed solution, with VBScript reading the info from WMI and Perl continually presenting the information in a Windows console. Despite the strange language mix, I think it stands as a good example of how to get at the kind of information you require (it should be quite possible to recode all of it in C++, of course).