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Load Average-----some conception to ask

Posted on 2001-07-17
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Last Modified: 2010-03-18
 i just found my linux6.2 server respond very slow,i use
"top" and found the the load average is about 24,and this
cause my sendmail stop,so i restart sendmail,the system is
ok,and the load average get down,SO,it seems that SENDMAIL
cause such a big load average,but /var/log/maillog say not
hing strange.
  first,i want to know if i found the load average is too
large,how to reduce it & how to check why this for??
  if you can give me some URL to introduce more about load
average or tuning system working,i will be very glad.
  (BTW,i use the "vmstat" to check this server,and,found
the "b" of "procs" is 5,but "r" & "w" is 0,it's sth happen
ded,right?)
 
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Question by:wingboad
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Expert Comment

by:MFCRich
ID: 6291785
Load average is the average number of processes that the scheduler has to choose from when it decides which process is going to run next. I go by the rule of thumb that load average should be lower than the number of CPUs in the box. A friend of mine uses the rule that if you have N CPUs then load average should be N-0.2 or lower.

The best way to reduce load average is to make sure you are not running anything you don't have to or schedule things to run at different times so they don't compete with each other.

You should also notice what the idle % is from top. It is sometimes a better indication of how heavily burden your system is. (Higher idle % means less burden)

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Author Comment

by:wingboad
ID: 6291970
 ok,the strange thing is the idle % is quite well,about 50
% or more left,but the load average is bigger than your rul
e said,i wondered when i restart the sendmail service,the f
irst number of Load Average(LA) is low,less than my CPU No.
but the second & third number is still 2 or 3 times than i
dle status. BTW,i don't run any strange or extreme services
on my server,all of them are normal and neccesary.
  also,how can i tune my system about LA,idle CPU,and free
MEMORY like that. thank you
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Accepted Solution

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MFCRich earned 10 total points
ID: 6300710
Using top you should be able to see both the total number of processes on your system and those that are running? Using shift-P will sort them by CPU usage.

The three numbers for load average represent your LA for different time periods. I'm not sure if these figure are exactly right but the first one is LA for last 5 seconds, the 2nd is for the last minute and the 3rd is for the last 10 minutes.

Also, some servers (like the apache web server) can fork a large number of children at start up. Look for processes with large numbers of instances running. The configuration file for the server in question should allow you to control this.

As for tuning LA, idle CPU, and memory the only real way to do this is not to run as many processes, buy a faster CPU, or buy more memory
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Author Comment

by:wingboad
ID: 6306996
ok,it seems that i can just do little about it,but,thanks
for your answer,i will accept it
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