Hi, Right, we have found the reason for this problem, at least on rhel6.2. This is due to rhel6 using a tickless kernel. Once this is disabled, everything works fine.
Found a kick off discussion on lkml about this issue - https://lkml.org/lkml/2011/8/22/67 Regards, Jon -----Original Message----- From: Kent, Jonathan D Sent: 28 March 2013 09:40 To: 'Mark Seger' Cc: [email protected] Subject: RE: [Collectl-interest] 0% Idle shown occasionally Funny you should say that about cpu stats not updating occasionally, got that :( I'll take a look at mpstat and figure out how this is working. A college looked at the code overnight hence the feedback on that. Cheers, Jon -----Original Message----- From: Mark Seger [mailto:[email protected]] Sent: 28 March 2013 09:08 To: Kent, Jonathan D Cc: [email protected] Subject: Re: [Collectl-interest] 0% Idle shown occasionally thanks jon, glad ti hear it's not a collectl problem. I am curious however about how mpstat does this as I though every tool measuring cpu usage went through /proc/stat. can you elaborate? btw - if you haven't seen it yet there is another problem with cpu stats coming with some kernels in that there is no activity and all percentages are reported as zero including idle! -mark On Thu, Mar 28, 2013 at 5:03 AM, Kent, Jonathan D <[email protected]> wrote: > Hi Mark, > > We've done some more digging and have found that mpstat using a different > approach to calc usage, whilst top doesn't. > > With top we see this issue as well, so its not a collect issue per se. So > for the moment I think this can be parked. > > Thanks, > > Jon > > -----Original Message----- > From: Mark Seger [mailto:[email protected]] > Sent: 27 March 2013 18:00 > To: Kent, Jonathan D > Cc: [email protected] > Subject: Re: [Collectl-interest] 0% Idle shown occasionally > > that's certainly a new one for me. can you run collectl for a small number > of samples, let's say 10, and play it back and still see 0s? > if could you send me the raw file and I'll take a closer look at the data? > > also, if you were to run 'collectl -sc -d4', it will print out what > it's reading from /proc/stat during each interval which may provide > additional clues > > -mark > > On Wed, Mar 27, 2013 at 10:59 AM, Kent, Jonathan D > <[email protected]> wrote: >> Hi, >> >> >> >> Seeing a problem across our rhel6.2 (kernel 2.6.32-220) servers with >> regards to cpu utilisation reporting. >> >> >> >> I'm see 0% idle regularly from the output of collectl at present. >> Test all versions from 3.4.0 to the latest version and they all show this >> behaviour. >> From looking at the Q&A package this is blamed on the kernel not >> supplying correct information in /proc/stat, yet I cannot see this >> issues. Equally when I run mpstat aside collectl, this returns the >> correct idle %, whilst collectl does not. >> >> >> >> Anyone else seen this? >> >> >> >> Regards, >> >> Jon >> >> >> >> >> >> >> >> >> >> >> >> This email is confidential and subject to important disclaimers and >> conditions including on offers for the purchase or sale of >> securities, accuracy and completeness of information, viruses, >> confidentiality, legal privilege, and legal entity disclaimers, >> available at http://www.jpmorgan.com/pages/disclosures/email. >> >> >> --------------------------------------------------------------------- >> - >> -------- Own the Future-Intel® Level Up Game Demo Contest 2013 >> Rise to greatness in Intel's independent game demo contest. >> Compete for recognition, cash, and the chance to get your game on >> Steam. $5K grand prize plus 10 genre and skill prizes. >> Submit your demo by 6/6/13. http://p.sf.net/sfu/intel_levelupd2d >> _______________________________________________ >> Collectl-interest mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/collectl-interest >> ------------------------------------------------------------------------------ Own the Future-Intel® Level Up Game Demo Contest 2013 Rise to greatness in Intel's independent game demo contest. Compete for recognition, cash, and the chance to get your game on Steam. $5K grand prize plus 10 genre and skill prizes. Submit your demo by 6/6/13. http://p.sf.net/sfu/intel_levelupd2d _______________________________________________ Collectl-interest mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/collectl-interest
