yahoo-eng-team team mailing list archive

[Daniel Berrange <1428551@xxxxxxxxxxxxxxxxxx>]

Mixing guests with huge pages and non-huge pages on the same host opens
up a huge can of worms, adding complexity to nova, and resulting in a
much unreliable system overall. With our current requirement that guests
using huge pages must run on hosts dedicated to the use of huge pages,
we can setup hosts such that nearly all RAM is allocated upfront to huge
pages, leaving just a little spare for non-guest RAM allocations.   To
allow effective mixing of huge page and non-hugepage guests on the same
host, things now need to be dynamic switching host RAM between being
huge page and non-hugepage based. The ability to reconfigure host RAM
from small pages to huge pages becomes increasingly problematic over
time as RAM becomes fragmented, to the point where you can have many GB
of free small pages, but be unable to turn them into huge pages.  As
such it is far preferrable to stick with the model that hosts are
dedicated to use of huge page guests only and huge pages allocated
upfront when the host is provisioned.

** Changed in: nova
       Status: Confirmed => Invalid

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https://bugs.launchpad.net/bugs/1428551

Title:
  creating vm may fails with large page vm and ordinary vm on the same
  numa node

Status in OpenStack Compute (nova):
  Invalid

Bug description:
  creating ordinary vm may fails with large page vm and ordinary vm on
  the same numa node.

  the following scene can reproduce the problem:
  1. Assumpt that a host with two numa nodes are used to create vm, and the memory of each numa node consists of 5GB huge page and 5GB ordinary page.

  2. create a vm with huge page  that use 3GB huge page memory in the
  host numa node 0. Now, the usable memory of the host numa node 0
  consists of 2GB huge page and 5GB ordinary page.

  3. At this time, we create an ordinary numa vm with 6GB and the
  NUMATopologyFilter filter may select the host numa node 0. If the host
  numa node 0 is selected, the libvirt will report OOM error.

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