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From Harikrishna Patnala <>
Subject Re: KVM memory overprovision breaking me
Date Tue, 28 Jan 2014 05:32:50 GMT
I think the way it was done is to guarantee minimum memory to that VM and upon demand it can
get upto the memory defined in service offering.
Say a vm with service offering 4Gb is deployed with overprovisioing factor 2, we guarantee
that vm should get minimum of 2GB (4GB/2) and if that VM is overloaded then it can get memory
unto max 4GB.
This is what it is showing vm definition
>>> <memory unit='KiB’>4GB</memory>
>>>  <currentMemory unit='KiB’>2GB</currentMemory>
"memory unit” is what it can get maximum.


On 28-Jan-2014, at 7:46 am, Marcus Sorensen <> wrote:

> Its an easy fix on the KVM side, just waiting to hear any objections.
> On Jan 27, 2014 6:11 PM, "Nux!" <> wrote:
>> On 28.01.2014 00:49, Marcus Sorensen wrote:
>>> So... I tried to use memory overcommit on KVM this week, and it blew
>>> up in my face. Apparently it's configured such that if I have a
>>> Service Offering of 4G, and I set memory overprovisioning to 2:1, the
>>> guest only actually gets configured with 2G. That's not how
>>> overprovisioning is supposed to work, IMO.
>>> Here's a vm definition with a 3:1 mem overprovision setting, which
>>> ensures that system vms don't work:
>>>  <memory unit='KiB'>262144</memory>
>>>  <currentMemory unit='KiB'>87040</currentMemory>
>>> Note currentMemory needs to be manually tuned if I ever want the vm to
>>> use/see more. This is more for live scaling (which is also broken
>>> because the guest could just rmmod virtio-balloon and see everything).
>>> I'd like to just rip out the code that is setting ballooning feature
>>> based on overprovisioning factor, but perhaps there was a reason this
>>> was done. From my point of view, if I give someone a service offering
>>> that says 4G, it should provide 4G, and if I can do memory
>>> deduplication on the backend to overprovision that's up to me to do.
>>> Overprovisioning should not be a divider on all service offerings.
>> Wow! I also thought, heck, KSM & thin qcows for the win! If
>> overprovisioning really "works" as you described then it can't possibly be
>> used for any commercial offering ...
>> This needs to get fixed.. Too late to see this in 4.3?
>> --
>> Sent from the Delta quadrant using Borg technology!
>> Nux!

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