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slow performance in guest Redhat Linux on VMware ESX

While running this script,
while [[ i -le $1 ]]
on a few RedHat 4 virtual guest machines, we noticed several different response times.  The worst case was on a guest OS which took over 40 seconds, whilst several other guest machines averaged around 4 or 5 seconds.  Would anyone be able to suggest the reason for such a wide discrepancy?

The slow machine runs on an ESX host with 4x3GHz Xeon cpu's, 30 GB of memory.  This physical host also runs 2 other guest systems, but all were relatively idle at the time of the test.  

On the slow machine, vmstat every 10 secs shows high cpu consumption (for such a simple script) and no memory shortfall (no swapping):

procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
 2  0      0 1444928 100896 402204    0    0     0     2 1011   104 51 21 28  0
 4  0      0 1443488 100896 402204    0    0     0    59 1017   217 75 25  0  0
 0  0      0 1446960 100896 402204    0    0     0    38 1014     93 34  9 57  0
 1  0      0 1447104 100896 402204    0    0     0    12 1012     89   7  2 91  0 <- end of test.

Any ideas much appreciated.

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1 Solution
jainesteerAuthor Commented:
Update: I should have mentioned that the timings were for counting up to 100,000 with the script.
does the guest have vmware-tools installed ?
jainesteerAuthor Commented:
On the vmware infrastructure client for this guest OS, it says VMWare Tools: OK.  
But "VMwareTools" is not in the guest OS rpm list.
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jainesteerAuthor Commented:
Ran vmware-tools on the guest (sorry, not used to vmware) and got version 3.5.0 build-110268.  
just right clicked on the guest on the virtual center or did an rpm -ivh of the vmware-tools rpm ?
follow this document to make sure you've done the whole thing...

and repeat the tests with the vmware tools service on
jainesteerAuthor Commented:
On the guest OS, the vmware service is already running ...

# service vmware-tools status
vmware-guestd is running
# ps -ef | grep -i vm
root      2625     1  1 Nov01 ?        00:53:02 /usr/sbin/vmware-guestd --background /var/run/vmware-guestd.pid
# cat /var/run/vmware-guestd.pid

So the performance test was run with the vmware tools service on.  I tried turning it off and back on again, but there is no difference in performance.
jainesteerAuthor Commented:
Problem resolved: the guest system was booting up with the ELhugemem Linux kernel instead of ELsmp. Set ELsmp as default in /etc/grub.conf and reboot.   Performance now normal!

Thks for your replies.

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