Re: CPU Utilization on IBM x3755

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Re: CPU Utilization on IBM x3755

Jeremy Chadwick-3
On Fri, Aug 15, 2008 at 02:03:06AM -0700, Won De Erick wrote:
> > The utilities you're using are correct (ps and top), but I don't know
> > why you're using top -S since it's pretty apparent you don't know how to
> > read the output.  :-)
> > thanks for the lights.
>
> I may not be well verse in interpreting the output, but I am using top -S to make other system processes (like pager, swapper) visible.
> I just wondered why the command name should be idle : cpu0, etc. instead of giving a little bit more descriptive name (like what you said, kernel thread bla bla). With this, it would be more understandable. An ordinary user like me could mistakenly interpret it as an "actual" process.

First and foremost, I'm not sure why you cross-posted this on 3 separate
lists (testing, performance, and hardware).  You probably should have
posted this on freebsd-questions, and if no response after a week or so,
again on freebsd-stable (although you're using FreeBSD 6.2).

It's generally shunned by the FreeBSD mailing list community to
cross-post to so many lists.  Just something to keep in mind for the
future.

> > You shouldn't be using -S if you're just interested in actual processes
> > on the UNIX machine itself.
>
> Then what should I use? I am interested in getting the detailed info to justify the %CPU idles and utilization.

Of the entire machine?  You can see that in top's header:

last pid: 84636;  load averages:  0.47,  0.14,  0.04 up 79+01:15:18  04:46:01
75 processes:  2 running, 70 sleeping, 3 stopped
CPU: 28.6% user,  0.0% nice,  8.2% system,  0.0% interrupt, 63.3% idle
Mem: 207M Active, 2433M Inact, 212M Wired, 91M Cache, 112M Buf, 57M Free
Swap: 8192M Total, 228K Used, 8192M Free

Regarding why you're adding up all the individual process statistics: I
can imagine they would vary a slight bit, but I cannot explain a 7%
variance.  Someone with more knowledge will have to assist there.

--
| Jeremy Chadwick                                jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |

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Won
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Re: CPU Utilization on IBM x3755

Won
>First and foremost, I'm not sure why you cross-posted this on 3 separate
>lists (testing, performance, and hardware).  You probably should have
>posted this on freebsd-questions, and if no response after a week or so,
>again on freebsd-stable (although you're using FreeBSD 6.2).

>It's generally shunned by the FreeBSD mailing list community to
>cross-post to so many lists.  Just something to keep in mind for the
>future.

Thanks for this reminder. I am testing my hardware against FreeBSD, and I just want to reach those people under the said areas (testing, performance, hardware) with the hope to get speedy response.

>> Then what should I use? I am interested in getting the detailed info to justify the %CPU idles and utilization.

>Of the entire machine?  You can see that in top's header:

>last pid: 84636;  load averages:  0.47,  0.14,  0.04 up 79+01:15:18  04:46:01
>75 processes:  2 running, 70 sleeping, 3 stopped
>CPU: 28.6% user,  0.0% nice,  8.2% system,  0.0% interrupt, 63.3% idle
>Mem: 207M Active, 2433M Inact, 212M Wired, 91M Cache, 112M Buf, 57M Free
>Swap: 8192M Total, 228K Used, 8192M Free

>Regarding why you're adding up all the individual process statistics: I
>can imagine they would vary a slight bit, but I cannot explain a 7%
>variance.  Someone with more knowledge will have to assist there.

Though the header could be conclusive, I should want the specific processes (or threads).
And come up with a list of breakdowns, like:

User (28.6%)
1. Program1 -- 20.0%
2. Program2 --  8.6%

System(8.2%)
1. SystemProcess1 -- X %
2. (and so on)         -- Y %

Then match this by adding up all individual processes statistics. And if I couldn't match, at least I could tell some factors that cause variance.
This variance has really struck my attention. When I run "top -SI", the result was:


last pid:  2746;  load averages:  0.20,  0.16,  0.10 up 0+00:07:38  
15:54:26
125 processes: 12 running, 100 sleeping, 16 waiting
CPU states:  
0.3% user,  0.0% nice,  6.4% system,  0.0% interrupt, 93.2% idle
Mem: 42M
Active, 18M Inact, 62M Wired, 20M Buf, 27G Free
Swap:
 
  PID USERNAME  THR PRI NICE   SIZE    RES STATE  C   TIME   WCPU
COMMAND
   17 root        1 171   52     0K    16K RUN    0   6:05 99.02%
idle: cpu0
   15 root        1 171   52     0K    16K CPU2   2   6:05 99.02%
idle: cpu2
   14 root        1 171   52     0K    16K CPU3   3   6:28 96.58%
idle: cpu3
   10 root        1 171   52     0K    16K CPU7   7   6:19 92.24%
idle: cpu7
   11 root        1 171   52     0K    16K CPU6   6   6:22 92.09%
idle: cpu6
   16 root        1 171   52     0K    16K CPU1   1   6:30 91.26%
idle: cpu1
   12 root        1 171   52     0K    16K CPU5   5   6:26 84.47%
idle: cpu5
   13 root        1 171   52     0K    16K CPU4   4   6:36 83.50%
idle: cpu4

The header says 12, but there were only 8 processes displayed. Sometimes it goes down to 10, but not 8.
Hope you can shed me more lights on this.


     
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Re: CPU Utilization on IBM x3755

Chris Elsworth
On Sat, Aug 16, 2008 at 01:18:18AM -0700, Won De Erick wrote:
 
> >Regarding why you're adding up all the individual process statistics: I
> >can imagine they would vary a slight bit, but I cannot explain a 7%
> >variance.  Someone with more knowledge will have to assist there.
>
> Though the header could be conclusive, I should want the specific processes (or threads).
> And come up with a list of breakdowns, like:
>
> Then match this by adding up all individual processes statistics. And if I couldn't match, at least I could tell some factors that cause variance.

At the bottom of man top, reformatted for email width:

        As with ps(1), things can change while top  is  collecting
        information for  an  update.  The picture it gives is only
        a close approximation to reality.

Could this explain the variations you are seeing? top never gives you
an accurate snapshot of what the system is doing at any one instant in
time, afaik.

--
Chris
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Won
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Re: CPU Utilization on IBM x3755

Won
In reply to this post by Jeremy Chadwick-3
On Sat, Aug 16, 2008 at 01:18:18AM -0700, Won De Erick wrote:

>> >Regarding why you're adding up all the individual process statistics: I
>> >can imagine they would vary a slight bit, but I cannot explain a 7%
>> >variance.  Someone with more knowledge will have to assist there.
>>
>> Though the header could be conclusive, I should want the specific processes (or threads).
>> And come up with a list of breakdowns, like:
>>
>> Then match this by adding up all individual processes statistics. And if I couldn't match, at least I could tell some factors that cause variance.
>
>At the bottom of man top, reformatted for email width:
>
>    As with ps(1), things can change while top  is  collecting
>    information for  an  update.  The picture it gives is only
>    a close approximation to reality.
>
>Could this explain the variations you are seeing? top never gives you
>an accurate snapshot of what the system is doing at any one instant in
>time, afaik.

>--
>Chris

I'm aware with this limitation as displayed using man top. But when I ran top -SI, I only got 8 processes out of 12 processes [actively] running as displayed on the header making it far from reality. I did this several times, restarting the machine, bootstrapping, etc, but I got same result.

I don't know what kernel threads are causing top -S to display the command as "idle: cpu0", "idle : cpu1", ... "idle:cpu7". Though Jeremy had mentioned them as simply kernel threads (due to lack of term), I should at least dig deeper on this matter and be able to specifically classify them.


     
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