LinuxQuestions.org
Latest LQ Deal: Complete CCNA, CCNP & Red Hat Certification Training Bundle
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 06-24-2011, 09:26 PM   #1
binary_pearl
Member
 
Registered: Jul 2007
Location: Chicago Illinois
Distribution: SLES 10 SP2/SP3, SLES 11 SP1, OpenSUSE, Sabayon, Gentoo, Fedora 14, RHEL 3/4/5/6
Posts: 98
Blog Entries: 3

Rep: Reputation: 23
Overall system impact when 1 cpu core is spiking when the rest are not


I'm fairly new as a Systems Administrator, but I have a fair amount of experience as a programmer/analyst in IT.

One of the problems that we struggle with in my current position is when should a (Linux) system send us an alert that something is wrong?

Specifically I'm referring to CPU alerts. One of our (bare-metal) systems has 8 cpu cores. We have HPSIM setup to send us an alert when a CPU is above a certain threshold (80% or more over X amount of time). In this case, one core (cpu 7) is spiking at near 100% usage, but the rest of cores are more or less at rest.

The question is, is this really an issue? Is the rest of the system still fine? My gut instinct tells me yes, it is. I assume that the process that's hogging one CPU is probably not multi-threaded, and there is nothing we can do about that. However I'm guessing that if a new process comes along, it would go to any of the other 7 freer processors.

Curious what you all think,

--Shaun

Last edited by binary_pearl; 06-24-2011 at 09:27 PM. Reason: Subtle modification in my English
 
Old 06-24-2011, 09:52 PM   #2
macemoneta
Senior Member
 
Registered: Jan 2005
Location: Manalapan, NJ
Distribution: Fedora x86 and x86_64, Debian PPC and ARM, Android
Posts: 4,593
Blog Entries: 2

Rep: Reputation: 332Reputation: 332Reputation: 332Reputation: 332
I think that you paid for a CPU, and ideally it should be running at 60-80% (all cores) at all times. When it's not, you're wasting your investment.

So no, one core running at 100% while 7 cores are idle (12.5% CPU utilization) is not a problem.
 
1 members found this post helpful.
Old 06-25-2011, 03:16 AM   #3
H_TeXMeX_H
LQ Guru
 
Registered: Oct 2005
Location: $RANDOM
Distribution: slackware64
Posts: 12,928
Blog Entries: 2

Rep: Reputation: 1288Reputation: 1288Reputation: 1288Reputation: 1288Reputation: 1288Reputation: 1288Reputation: 1288Reputation: 1288Reputation: 1288
I think if the multi-core scheduler is enabled in the kernel it should switch the process between cores to prevent 1 core from getting consistently hotter than the others. At least, this is what it does on my system when the process is not threaded.
 
1 members found this post helpful.
Old 06-25-2011, 06:14 AM   #4
MTK358
LQ 5k Club
 
Registered: Sep 2009
Posts: 6,443
Blog Entries: 3

Rep: Reputation: 721Reputation: 721Reputation: 721Reputation: 721Reputation: 721Reputation: 721Reputation: 721
Quote:
Originally Posted by binary_pearl View Post
I assume that the process that's hogging one CPU is probably not multi-threaded, and there is nothing we can do about that. However I'm guessing that if a new process comes along, it would go to any of the other 7 freer processors.
That's correct.
 
1 members found this post helpful.
Old 06-25-2011, 02:49 PM   #5
jefro
Moderator
 
Registered: Mar 2008
Posts: 17,960

Rep: Reputation: 2678Reputation: 2678Reputation: 2678Reputation: 2678Reputation: 2678Reputation: 2678Reputation: 2678Reputation: 2678Reputation: 2678Reputation: 2678Reputation: 2678
I'd look to why either some software has been dedicated to that core or why it is performing above the other's.

Some applications would use a single core to act as a control for work sent to other cores. Many high end or special use apps could do that.

I find it odd that it is core 7 and not core 0 or 1 depending on naming.
 
1 members found this post helpful.
Old 06-26-2011, 10:21 AM   #6
binary_pearl
Member
 
Registered: Jul 2007
Location: Chicago Illinois
Distribution: SLES 10 SP2/SP3, SLES 11 SP1, OpenSUSE, Sabayon, Gentoo, Fedora 14, RHEL 3/4/5/6
Posts: 98
Blog Entries: 3

Original Poster
Rep: Reputation: 23
Thanks all, I'll check to make sure multi-treading options in the kernel config are set. I imagine they are, it's a RHEL-4 system I believe.

I think cpu 7 was spiked because there was another process earlier that was spiking cpu 0. The new process probably went to cpu 7, and then by the time I looked it at again, the process on cpu 0 had finished. (I'm using `top` to see which cores are spiking).

This information will help me go back to the senior admin I work with and tell him it's ok, we don't need to be woken up at 2am because one core is spiking

--Shaun
 
  


Reply


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
top CPU% reported over 100% on single core system alburdet619 Linux - General 6 07-15-2010 03:24 PM
Single cpu-core used on multicore system when processes communicate with pipe merijnv Linux - Kernel 3 04-10-2009 09:17 PM
system clock runs at twice speed on dual core cpu samkraju Fedora 4 10-08-2007 06:09 PM
LXer: Open Source Impact on Software Innovation Outweighs Impact on ... LXer Syndicated Linux News 0 08-15-2006 01:54 PM
Installing rest of Fedora Core - 4 packages libregeek Fedora - Installation 3 11-19-2005 07:51 AM

LinuxQuestions.org > Forums > Linux Forums > Linux - General

All times are GMT -5. The time now is 02:31 AM.

Main Menu
Advertisement
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
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration