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From Bharat Kumar <bharat.ku...@citrix.com>
Subject Re: Incorrect Memory Usage in Dashboard When Overprovisoined
Date Fri, 17 Apr 2015 05:35:35 GMT
Hi ,

This doc should make the memory calculations clear to you.

https://cwiki.apache.org/confluence/display/CLOUDSTACK/CPU+and+RAM+Overcommit

Thanks,
Bharat.

On 16-Apr-2015, at 3:24 pm, 蔡高扬 <CAIGAOYANG889@pingan.com.cn<mailto:CAIGAOYANG889@pingan.com.cn>>
wrote:

      When I changed the value of “mem.overprovisioning.factor” in a cluster, i.e. from
1 to 2, the used memory value in dashboard also changed (in this example, doubled) as well
as total momory. After I shut down VMs in the cluster and start them, memory usage became
correct.

      I found the code calculating the used momory but couldn’t understand the way to calculating
and updating this value.

In com.cloud.capacity.CapacityManagerImpl.updateCapacityForHost(Host):
===================================================================
usedMemory += ((so.getRamSize() * 1024L * 1024L)/ramOvercommitRatio)*clusterRamOvercommitRatio;
===================================================================

      In the code above, clusterRamOvercommitRatio updates instantly after overprovisioning
factor sets, but ramOvercommitRatio only updates according to clusterRamOvercommitRatio when
VM starts. This leads to inconsistency between the two variables.
      So my question is:

1.      Why calculating usedMemory in such way (devided by ramOvercommitRatio and then multiplied
clusterRamOvercommitRatio)?

2.      Why NOT updating ramOvercommitRatio when overprovisioning factor changes, until when
VM starts?

3.      How to fix incorrect memory usage without restarting VMs ?



Thanks.

Kelvin Cai,
Ping An Technology (Shenzhen) Co., Ltd. | Infrastructure.





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