Background jobs on Unix impact on System Performance
Posted on February 6th, 2010 in Oracle on Linux background jobs in Unix, command to check current system load, job priority, nice command, renice command
Is your background jobs on Unix impact on System Performance?
Yes, but it depends upon the priority of the job and how much RAM they require to run. Large jobs like you are downloading a huge file from the web, can consume immense amount of RAM which can be very painful for your system performance . If your job requires too much RAM, the system CPU will be wasting a lot of time swapping memory to and from disk rather than executing the jobs.
Secondly ,other variable affects your system performance is job priority. If your jobs run at low priority, they will be executed at the system’s leisure time and your system performance will not affected . If they run at normal priority, they will increase the competition for resources and finally performance of your may be degraded. On a heavily loaded system, jobs should only be put into the background at low priority, using the “nice” (Which is very nice to balance your system performance) command. Very simple to use nice command. Just put “nice” before your regular command.
For example, if you normally execute your program with the following
myscript < inputfile > outfile &
where myscript reads from ” inputfile” and writes to ” outfile ” . To run the same in low priority you should use as follows :
nice -19 myscript < inputfile > outfile &
There is a command to determine current load of your system , which is “uptime” command .
The output of the “uptime” command looks like as follows
14:49:07 up 192 days,4:15,105 users,load average: 0.16,0.52,0.34
Have you noticed three numbers at the right of the resulting report ? These three numbers indicate the load of your system . If the first number of the three number is more than 3, then background jobs only initiated with low priority (niced)
“renice” command
To change the priority of a job , which is already running, you can use “renice” command.
For example,If one job is already running, you can check the process id of the job using “ps” or “ps -u ” command. suppose the process id of the job is 12337. Run the job in low priority using the following command
renice -19 12337
Read about job Control on UNIX systems
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