How to use .. QNX Momentics Application Profiler?
I'd like to profile my (multi-threaded) application in terms of timing. Certain threads are supposed to be re-activated frequently, i.e. a thread executes its main job once every fixed time interval. In other words, there's a fixed time slice in which all the threads a getting re-activated.
More precisely, I expect certain threads to get activated every 2ms (since this is the cycle period). I made some simplified measurements which confirmed the 2ms to be indeed effective.
For the purpose of profiling my app more accurately it seemed suitable to use Momentics' tool "Application Profiler". However when I do so, I fail to interpret the timing figures that I selected. I would be interested in the average as well in the min and max time it takes before a certain thread is re-activated. So far it seems, the idea is to be only able to monitor the times certain functions occupy. However, even that does not really seem to be the case. E.g. I've got 2 lines of code that are put literally next to each other:
if (var1 && var2 && var3) var5=1; takes 1ms (avg)
if (var4) var5=0; takes 5ms (avg)
What is that supposed to tell me?
Another thing confuses me - the parent thread "takes" up 33ms on avg, 2ms on max and 1ms on min. Aside the fact that the avg shouldn't be bigger than max (i.e. even more I expect avg to be not bigger than 2ms - since this is the cycle time), it's actually increasing the longer I run the the profiling tool. So, if I would run the tool for half an hour the 33ms would actually be something like 120s. So, it seems that avg is actually the total amount of time the thread occupies the CPU.
If that is the case, I would assume to be able to offset against the total time using the count figure which doesn't work either. Mostly due to the figure being almost never available - i.e. there is only as a separate list entry (for every parent thread) called which does not represent a specific process scope.
So, I read QNX community wiki about the "Application Profiler", incl. the manual about "New IDE Application Profiler Enhancements", as well as the official manual articles about how to use the profiler tool.. but I couldn't figure out how I would use the tool to serve my interest.
Bottom line: I'm pretty sure I'm misinterpreting and misusing the tool for what it was intended to be used. Thus my question - how would I interpret the numbers or use the tool's feedback properly to get my 2ms cycle time confirmed?
Additional information
- CPU: single core
- QNX SDP 6.5 / Momentics 4.7.0
- Profiling Method: Sampling and Call Count Instrumentation
- Profiling Scope: Single Application
- I enabled "Build for Profiling (Sampling and Call Count Instrumentation)" in the Build Options1
The System Profiler should give you what you are looking for. It hooks into the micro kernel and lets you see the state of all threads on the system. I used it in a similar setup to find out what our system was getting unexpected time-outs. (The cause turned out to be Page Waits on critical threads.)