I'm running into a strange issue on Vista with the Performance monitoring API. I'm currently using code that worked fine on XP/2k, based around PdhGetFormattedCounterValue(). I start out using PdhExpandWildCardPath to expand the counters (I'm interested in overall network statistics), the counters I'm looking at are:
\\Network Interface(*)\\Bytes Received/sec \\Network Interface(*)\\Bytes Sent/sec \\Processor(_Total)\\% Processor Time
The problem is that on their first call they return PDH_INVALID_DATA, I don't think this is a problem, since if I query it again I will start getting data without the error. The problem is this – while the processor time is worked exactly as expected, neither of the network interface counters are returning anything – just 0 all the time. I verified using Perfmon that they are reporting data normally, so I'm at a loss as to what might be the issue. I caught this at MS:
http://support.microsoft.com/?scid=kb%3Ben-us%3B287159&x=11&y=9
But I'm not interested in multi-language for my task, so I don't think this is relevant. I will see if I can come up with some basic code showing exactly what I'm doing, but nothing is returning anything strange, and it worked on XP/2k, so I suspect something changed under the hood. Thanks!
Best Answer
It turns out the issue was that the network interfaces are both wildcards, whereas the Processor one is actually already rolled up by the performance monitoring. What I didn't realize was that it PdhExpandWildCardPath didn't return something directly usable by PdhAddCounter. By this I mean that if ExpandWildCard returns 3 expanded matches, they come back as a null separated strings - I understood this, but I had assumed that AddCounter would be effectively create a counter containing all three. Nope, reality is I needed to break up each path and request it individually from AddCounter, then roll up the results manually when I get them.
Hopefully this helps someone else to avoid the same mistake I made with less frustration. ;)