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?
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