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How to interpret TOP

 
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# 1  
Old 03-27-2008
How to interpret TOP
Hi,


So I am new to Unix, and I need to check the performance of some apps I am running. But I don't know how to interpret the output from TOP.

Could somebody please explain the difference between the different values. And also explain how I can have a process which has a %CPU > 100?


Thanks
# 2  
Old 03-27-2008
Quote:
Originally Posted by dj_jay_smith
So I am new to Unix, and I need to check the performance of some apps I am running. But I don't know how to interpret the output from TOP.

Could somebody please explain the difference between the different values.
this should be the starter for you: man top
# 3  
Old 03-27-2008
Quote:
Originally Posted by Yogesh Sawant
this should be the starter for you: man top
And where does it say what is meant by Load, Nice, User, block, swait, etc and how a process can be over 100% in the man page?

Because I can't find it!
# 4  
Old 05-23-2009
Quote:
Originally Posted by dj_jay_smith
and where does it say what is meant by load, nice, user, block, swait, etc and how a process can be over 100% in the man page?

Because i can't find it!
+1 Smilie
# 5  
Old 05-23-2009
Quote:
Originally Posted by dj_jay_smith
And where does it say what is meant by Load, Nice, User, block, swait, etc and how a process can be over 100% in the man page?

Because I can't find it!

Sometimes the man pages aren't that great, but at least you started there! Smilie Anyway...

A process can be over 100% if it is running on a multi-core processor.

A Nice value is essentially the priority of a process. A lower number means a higher priority. man renice for an explanation of nice.

swait is the % of time that the OS is waiting for I/O to complete. A high value means there's a bottleneck somewhere and processes are waiting for attention, so to speak.

I'm not totally sure about "block" and "load" so I will defer to someone else on that one. Hope that helps a little.
# 6  
Old 05-23-2009
Oh snap, that's an old post. Just noticed that.
# 7  
Old 05-23-2009
You can't find it? Did you possibly delete the man pages from the system? Or just that one?

Code:
%CPU  --  CPU usage
          The  taskâs  share of the elapsed CPU time since the last screen update, expressed as a percentage of total CPU time.  In a true SMP
          environment, if âIrix modeâ is Off, top will operate in âSolaris modeâ where a taskâs cpu usage will be divided by the total  number
          of CPUs.  You toggle âIrix/Solarisâ modes with the âIâ interactive command.

Copied directly from the man page on 'top'. It is the second section of the man page, specificaly 2a "2. FIELDS / Columns - 2a. DESCRIPTIONS of Fields".

Just testing really quick on a CentOS 5.2 box, using top cd1 I noticed something at between 80 and 100 on cpu. So I did shift + i (capital i), and it turned Irix mode off (apparently it is on by default), and then it showed the usage of those at about 12% or so. Yeah..
 
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