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Linux server performance issue

Posted on 2010-08-19
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Last Modified: 2013-12-16
I have a server running cacti with 2 cpu & 2 gb memory. It is showing me 100% cpu utilized for some perl scripts getting information from storage luns. memory also 98-99 % utilized. I tried to tune vm.swappiness to 80, as i thought that the memory is less so swapping the pages out may help, but still the performance is killing. kindly let me know wht all parameters can be checked to tune the linux system. I am using nmon tool.
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Question by:pankajgadhari
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by:savone
ID: 33476362
I would check the perl scripts.  Seems like one of them might be in some kind of infinite loop.

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by:pankajgadhari
ID: 33476477
These perl scripts are standard template. We are in a process of checking the scripts, but apart from that, is there any kernel parameters which we can tune to increase the performance based on output of iostat, vmstat or sar.
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by:pankajgadhari
ID: 33476608
[root@server ~]# sar -B 2 3
Linux 2.6.18-164.el5 (epnetmon4.vvtv.com)       08/19/2010

10:45:17 AM  pgpgin/s pgpgout/s   fault/s  majflt/s
10:45:19 AM   8450.25     38.19   8664.82    371.86
10:45:21 AM   8078.00    220.00   8401.50    367.00
10:45:23 AM   7990.00     82.00   8307.00    389.00
Average:      8172.29    113.52   8457.43    375.96
[root@server ~]# cat /proc/sys/vm/swappiness
60

Sar is showing that the system is swaping very much, i changed the value from 60 to 80 yesterday without reboot & today i changed it back to 60 without reboot, as I was not getting any performance gain. kindly suggest. Do i need to tune vm.swappiness & vm.overcommit_memory for performance gaining. kindly suggest
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ssapkota earned 200 total points
ID: 33478089
Okay it is clear that those perl-process are memory-hog.
In this case you might wanna tune following kernel-params:
vm.overcommit_memory=2
and
increase vm.overcommit_ratio to somewhat like 80.

Regarding vm.swapiness. Remember "The higher the vm.swappiness value, the more the system will swap." And if the system swaps more, its obviously going to hit the system performance. Keep it low (20-40) if most of the memory is consumed by active process.

You might wanna go through the following articles:
http://www.linuxvox.com/2009/10/what-is-the-linux-kernel-parameter-vm-swappiness/
http://www.win.tue.nl/~aeb/linux/lk/lk-9.html

And remember -- only modify one vm parameter at a time and monitor the performance.
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Assisted Solution

by:madunix
madunix earned 150 total points
ID: 33486148
you could  try some of the following settings (mentioned above)
vm.min_free_kbytes = 16384
vm.overcommit_memory = 2
vm.overcommit_ratio = 75
vm.lower_zone_protection = 100
vm.vfs_cache_pressure = 10000
http://www.linuxinsight.com/proc_sys_vm_overcommit_memory.html
http://www.redhat.com/magazine/001nov04/features/vm/
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by:Michael W
Michael W earned 150 total points
ID: 33487179
Also, as root, try flushing the pagecache and slabcache:

echo 3 > /proc/sys/vm/drop_caches


/etc/sysctl.conf configuration way:

vm.drop_caches = 3
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by:pankajgadhari
ID: 33526437
Met the expectation
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