099a6f63af
The numa_fit_instance_to_host algorithm tries all the possible host cell permutations to fit the instance cells. So in worst case scenario it does n! / (n-k)! _numa_fit_instance_cell calls (n=len(host_cells) k=len(instance_cells)) to find if the instance can be fit to the host. With 16 NUMA nodes host and 8 NUMA node guests this means 500 million calls to _numa_fit_instance_cell. This takes excessive time. However going through these permutations there are many repetitive host_cell, instance_cell pairs to try to fit. E.g. host_cells=[H1, H2, H2] instance_cells=[G1, G2] Produces pairings: * H1 <- G1 and H2 <- G2 * H1 <- G1 and H3 <- G2 ... Here G1 is checked to fit H1 twice. But if it does not fit in the first time then we know that it will not fit in the second time either. So we can cache the result of the first check and use that cache for the later permutations. This patch adds two caches to the algo. A fit_cache to hold host_cell.id, instance_cell.id pairs that we know fit, and a no_fit_cache for those pairs that we already know that doesn't fit. This change significantly boost the performance of the algorithm. The reproduction provided in the bug 1978372 took 6 minutes on my local machine to run without the optimization. With the optimization it run in 3 seconds. This change increase the memory usage of the algorithm with the two caches. Those caches are sets of integer two tuples. And the total size of the cache is the total number of possible host_cell, instance_cell pairs which is len(host_cell) * len(instance_cells). So form the above example (16 host, 8 instance NUMA) it is 128 pairs of integers in the cache. That will not cause a significant memory increase. Closes-Bug: #1978372 Change-Id: Ibcf27d741429a239d13f0404348c61e2668b4ce4
OpenStack Nova
OpenStack Nova provides a cloud computing fabric controller, supporting a wide variety of compute technologies, including: libvirt (KVM, Xen, LXC and more), Hyper-V, VMware, OpenStack Ironic and PowerVM.
Use the following resources to learn more.
API
To learn how to use Nova's API, consult the documentation available online at:
For more information on OpenStack APIs, SDKs and CLIs in general, refer to:
Operators
To learn how to deploy and configure OpenStack Nova, consult the documentation available online at:
In the unfortunate event that bugs are discovered, they should be reported to the appropriate bug tracker. If you obtained the software from a 3rd party operating system vendor, it is often wise to use their own bug tracker for reporting problems. In all other cases use the master OpenStack bug tracker, available at:
Developers
For information on how to contribute to Nova, please see the contents of the CONTRIBUTING.rst.
Any new code must follow the development guidelines detailed in the HACKING.rst file, and pass all unit tests.
Further developer focused documentation is available at:
Other Information
During each Summit and Project Team Gathering, we agree on what the whole community wants to focus on for the upcoming release. The plans for nova can be found at: