Determining cause behind high load average


 
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# 1  
Old 01-06-2010
Determining cause behind high load average

How to determine what is causing high load average in a system?
# 2  
Old 01-06-2010
cpu load - start with the top command, see what processes are consuming resources.
top is a snapshot - sar can also be used to get data over a longer period. Read the man page on sar.

---------- Post updated at 14:25 ---------- Previous update was at 14:23 ----------

You do realize that what counts is not an avg. 98% cpu utilization vs and avg. of 25% --but how many processes are in a cpu wait state. Those 'starved' processes are the ones that run too slowly. Things can be just fine with cpu load averages near 100%.
# 3  
Old 01-06-2010
Do the following:

ps aux | awk '{print $11}' | sort | uniq -c | sort -nk1 | tail -n5
ps aux | awk '{print $1}' | sort | uniq -c | sort -nk1 | tail -n5

Both of those will provide information on how many threads are running of one service or user.

top will provide information in real time regarding CPU% Mem% Time%

ps auxf will show child processes of an instance, which you may want to look into. For example if an apache instance has 500 child threads of php for 1 user, you can just tail the apache log for more information on what's causing it.

I would also suggesting looking into both iotop and iftop -i eth0 (depending on your device) to see if there's any saturation over io or the network.
# 4  
Old 01-06-2010
There are plenty of tools that will tell what the loading of your system is but not what particular process or branch of processes are the major culprits!
A script that runs something like "top -b -n 1" every minute (called from cron) or so into a log file might show you what is going on.
 
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