High load (25% system) on 6450, 1+1+1=3 ;-)

Vsevolod Ilyushchenko simonf at cshl.edu
Tue Mar 19 12:23:00 CST 2002


Dirk,

I would not deny you are right, but would not SAS then take up more than
10% of CPU time in the top output? And would not an I/O heavy system force
the CPU be mostly in the I/O and not system mode?

The reason I even ask about it is that it's not the first time I observe
such behavior on Linux systems. Is this normal for a heavily I/O-ing system
to have huge load but no processes visibly responsible for it?

Simon

Dirk Wetter wrote:
> 
> well, if sar reports system time, top is showing something in D state
> and i17 shows disk activity, guess you found it. you could also
> use iostat btw.
> 
> look for processes having open files on partitions of this disk (lsof
> is good for that).
> 
> On Tue, 19 Mar 2002, Vsevolod Ilyushchenko wrote:
> 
> > Hi,
> >
> > I am running stock 2.4.17 on a 6450. I have recently upgraded to 4 CPUs,
> > and soon after that I began to see high load. Today it varies from 5 to 8,
> > and it's not an accounting fluke - the system is very slow.
> >
> > The maddening thing is that I cannot figure out what's causing it. Top does
> > not show any CPU-hogging programs. The only abnormal thing that I saw in
> > the sar output is consistently high system time percentage:
> >
> > 12:00:11 AM       CPU     %user     %nice   %system     %idle
> > 12:10:00 AM       all      2.77      0.42     26.22     70.60
> > 12:20:09 AM       all      2.47      0.01     25.80     71.72
> > 12:30:00 AM       all      2.39      0.01     25.98     71.62
> > 12:40:10 AM       all      2.48      0.01     25.74     71.77
> > 12:50:24 AM       all      2.49      0.01     25.86     71.64
> >
> > My suspicions are on SAS running some user batch programs. Most of the time
> > it's in the D state according to top, but since it constantly updates a
> > file in /var/tmp, it's not dead.
> >
> > I see somewhat high disk activity on interrupt 17:
> >
> > (from /proc/interrupts:
> >  17:   15878552   15873368   15886390   15879782   IO-APIC-level  aic7xxx
> > )
> >
> > 12:00:11 AM  CPU  i000/s  i001/s  i002/s  i014/s  i017/s  i018/s  i026/s
> > 12:10:00 AM    0   25.16    0.00    0.00    0.00  199.71    0.00    1.74
> > 12:10:00 AM    1   24.99    0.00    0.00    0.00  198.40    0.00    1.78
> > 12:10:00 AM    2   25.34    0.00    0.00    0.00  202.26    0.00    1.77
> > 12:10:00 AM    3   24.51    0.00    0.00    0.00  197.82    0.00    1.70
> > 12:20:09 AM    0   24.96    0.00    0.00    0.00  198.46    0.00    1.16
> > 12:20:09 AM    1   24.95    0.00    0.00    0.00  198.56    0.00    1.16
> > 12:20:09 AM    2   24.81    0.00    0.00    0.00  198.47    0.00    1.15
> >
> > But this disk activity may just be the indicator of SAS writing its file.
> >
> > Here is free output showing that memory is fine:
> >
> >              total       used       free     shared    buffers     cached
> > Mem:       3996696    3890456     106240          0      75036    3300428
> > -/+ buffers/cache:     514992    3481704
> > Swap:       530104      32792     497312
> >
> > I will be very grateful for any suggestions.
> >
> > Simon
> > --
> > Simon (Vsevolod ILyushchenko)   simonf at cshl.edu
> > http://www.simonf.com          simonf at simonf.com
> >
> > "A man who feels himself a citizen of the world whose
> > loyalty is to the human race and to life, rather than
> > to any exclusive part of it; a man who loves his country
> > because he loves mankind, and whose judgement is not
> > warped by tribal loyalties." Erich Fromm
> >
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-- 
Simon (Vsevolod ILyushchenko)   simonf at cshl.edu   
http://www.simonf.com          simonf at simonf.com 

"A man who feels himself a citizen of the world whose 
loyalty is to the human race and to life, rather than 
to any exclusive part of it; a man who loves his country 
because he loves mankind, and whose judgement is not 
warped by tribal loyalties." Erich Fromm




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