ec74cc688e
Take three hosts, one with a single PCI device, one with many PCI devices, and one with no PCI devices. Nova should prioritise these differently based on the demands of the instance. If the instance requests a single PCI device, then the first of the hosts should be preferred. Similarly, if the instance requests multiple PCI devices, then the second of these hosts would be preferred. Finally, if the instance does not request a PCI device, then the last of these hosts should be preferred. While the first and second of these cases is already somewhat handled by the NUMA topology filter (which will ensure the correct number and type of PCI devices are available on the hosts), there is nothing to stop a instance that *does not* require PCI devices from occupying space on one of the few hosts that *does* have free PCI devices. The PCIWeigher is designed to keep hosts with PCI device(s) as free as possible, to best ensure they can satisfy requests from instances with PCI requirements when called upon. This change ensures (a) an instance with PCI requirements has the best possible chance of scheduling successfully and (b) an instance without these requirements won't clog up hosts that have these valuable resources. Change-Id: I04bf7e6b8324dcac6c93b0cb69c38c30fb05be56 Partially Implements: blueprint reserve-numa-with-pci |
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