LinuxQuestions.org
Welcome to the most active Linux Forum on the web.
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - General
User Name
Password
Linux - General This Linux forum is for general Linux questions and discussion.
If it is Linux Related and doesn't seem to fit in any other forum then this is the place.

Notices

Reply
 
Search this Thread
Old 07-12-2010, 09:23 AM   #1
alburdet619
LQ Newbie
 
Registered: Jun 2010
Posts: 13

Rep: Reputation: 0
top CPU% reported over 100% on single core system


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?
 
Old 07-12-2010, 10:27 AM   #2
yooy
Senior Member
 
Registered: Dec 2009
Posts: 1,143

Rep: Reputation: 133Reputation: 133
I have heard of some ati processors that have hidden cores that can be overclocked.. what kind of processor do you exactly have..

It could be also bad reporting..(no good sync..)
 
Old 07-12-2010, 12:20 PM   #3
alburdet619
LQ Newbie
 
Registered: Jun 2010
Posts: 13

Original Poster
Rep: Reputation: 0
We have a 1.0 GHz Celeron M processor.
 
Old 07-12-2010, 08:01 PM   #4
syg00
LQ Veteran
 
Registered: Aug 2003
Location: Australia
Distribution: Lots ...
Posts: 12,278

Rep: Reputation: 1028Reputation: 1028Reputation: 1028Reputation: 1028Reputation: 1028Reputation: 1028Reputation: 1028Reputation: 1028
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.
 
Old 07-13-2010, 07:04 AM   #5
alburdet619
LQ Newbie
 
Registered: Jun 2010
Posts: 13

Original Poster
Rep: Reputation: 0
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?
 
Old 07-13-2010, 06:17 PM   #6
syg00
LQ Veteran
 
Registered: Aug 2003
Location: Australia
Distribution: Lots ...
Posts: 12,278

Rep: Reputation: 1028Reputation: 1028Reputation: 1028Reputation: 1028Reputation: 1028Reputation: 1028Reputation: 1028Reputation: 1028
Is it truly single core - what about hiper-thread ?. Check /proc/cpuinfo to be sure.
Are you running in a virtualised guest ?.
 
Old 07-15-2010, 03:24 PM   #7
alburdet619
LQ Newbie
 
Registered: Jun 2010
Posts: 13

Original Poster
Rep: Reputation: 0
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.
 
  


Reply

Tags
cpu, cpuusage, top


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Dual core cpu, 2 scp processes, 100% iowait. john.daker Linux - Newbie 4 06-22-2009 08:16 AM
Single cpu-core used on multicore system when processes communicate with pipe merijnv Linux - Kernel 3 04-10-2009 09:17 PM
SMP system - use a single CPU during boot bromanescu Programming 4 10-18-2008 04:29 PM
SYstem bogged down since last reinstall... CPU at 100%? kdupuy9 Suse/Novell 5 07-17-2007 08:02 PM
top says SoftIRQ is taking 100% of one CPU RichDygert Linux - Newbie 0 10-09-2006 12:47 PM


All times are GMT -5. The time now is 05:10 AM.

Main Menu
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
identi.ca: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration