I think I found an answer myself, albeit an unreliable one.
The Process Explorer utility for Windows measures disk I/O - by volume and by occurences. So there's a rough way to get the answer: say a process performs 3 000 reads in 30 minutes, whilst using 2% of CPU during that time (assuming a single core CPU). So the process has used 36000ms of CPU time, divided into ~5200 blocks (this is the unreliable part - the process in all proabbility does not use the whole of the time slot, so I'll just divide by half the time slot). 3000/5200 gives a 57% chance of reading data after using the CPU.
I hope I did not misunderstand the "reads" statistic in Process Explorer.