I am using this class as a base class for a category of tests that launch a process and give it some input and wait for it to become idle before giving it more input.
public abstract class TestProcessLaunchingBase
{
protected PerformanceCounter PerfCounter { get; set; }
protected void WaitForProcessIdle()
{
while (true)
{
float oldValue = PerfCounter.NextValue();
Thread.Sleep(1000);
float nextValue = PerfCounter.NextValue();
if (nextValue == 0)
break;
}
}
protected void FindSpawnedProcessPerfCounter(int processId)
{
PerformanceCounterCategory cat = new PerformanceCounterCategory("Process");
string[] instances = cat.GetInstanceNames();
foreach (string instance in instances)
{
using (PerformanceCounter cnt = new PerformanceCounter("Process", "ID Process", instance, true))
{
int val = (int)cnt.RawValue;
if (val == processId)
{
PerfCounter = new PerformanceCounter("Process", "% Processor Time", instance);
break;
}
}
}
Assert.IsNotNull(PerfCounter, "Failed to perf counter");
}
}
These tests occasionally fail because PerfCounter.NextValue()
throws an
System.InvalidOperationException
Instance 'foobar#2' does not exist in the specified Category
It seems like the instance name of the performance counter is not persistent.
If there are three foobar processes they might have instance names
- foobar pid 5331
- foobar #1 pid 5332
- foobar #2 pid 5333
It seems like if pid 5332 exits foobar #2 becomes foobar #1.
Questions:
-
Is this a documented behavior ? Can you not persistent a performance counter ? Do you have to look it up every time ?
-
Alternatively, is there a performance counter that can give Processor Time for all processes named foobar
Best Answer
I already faced this issue in the past. The
ProcessName#InstanceNumber
pattern for the instance name was clearly a poor choice from Microsoft, you know why :)So basically you have two choices:
1) Create a new
PerformanceCounter
instance each time, using yourFindSpawnedProcessPerfCounter
method.2) Follow the steps described in KB281884 to change the pattern from
ProcessName#InstanceNumber
toProcessName_ProcessID
.The problem of the first solution is that it requires some CPU time to build a new instance each time.
The problem of the second solution is that the registry modification also impacts all programs that are also using this performance counter. And it requires to modify the registry before launching your app.
Last option you have, is to not use Performance counters at all. If you are only interested in the
ProcessorTime
information, there are some Kernel32 functions you could call using P/Invoke to retrieve it.EDIT:
The
Process
class also providesUserProcessorTime
andPrivilegedProcessorTime
(kernel processor time) properties. Both return aTimeSpan
instance (= amount of time), so to retrieve a percentage of processor time, you'll have to do some computation by yourself (involving the refresh period and the processor times).