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Hi all, I am running CPU tests on a radio controller to determine max simultanious calls. A tool using top was developed so that we could get a good look at what exactly was happening on the process level, however we are mainly interested in one object running on the box.
The box has a single core Celeron processsor running the Wind River Linux platform. The CPU usage from my object is frequently spiking over 100%. Doing some research online so far has led me to the fact that a multicore processor can do this however I have found no mention of a single core processor displaying this behavior. Can someone please explain this?
An artifact of sampling data. Top runs through /proc/<pid>/* - i.e. it reads all of them sequentially. All takes some time, and strictly speaking the data is all from different times. Then it reads the total system consumption over the period, and does some math.
Did you ever get collectl working ?. Even that will suffer somewhat, but the granularity is much better. Another option would be to do your own measurement - pull the numbers for only your pid, and the system wide, do the math after. Will still be some disparity - unavoidable.
I did get collectl to work on our operating system however the focous at work shifted at that point and I never got to use it. When the issue came back up someone had already made the top logging program and I was asked to use that (work politics, don't ask lol).
Regarding my earlier problem with differences between vmstat and ps, it turns out ps takes averages since boot so it would never match with vmstat.
Sadley though syg00 it isn't an option to just redo these tests with another tool. The top logger data looks good, i'm just confused about the 100%+ readings. Is it possibly because the object that i'm interested in is a multi-thread process? Logically that still doesn't make since... one core can only get to 100% even with multi-threading right?
Okay everyone, I am happy to report that the problem has been solved, and I'm sure you will all be happy to hear that it was no fault of Linux but of Microsoft. We were taking a snap shot of top every 0.8 seconds. The pivot table which was used to combine all the logs of top was not taking into account the points of a second and was combining all readings for a given second into one reading. This is the reason for my 100%+ readings. Thank you all for you work on this, I truly appreciate it and I'm sorry if I have wasted your time.