66 lines
2.7 KiB
Python
66 lines
2.7 KiB
Python
# Copyright (c) 2016, Red Hat Inc.
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# All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""
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PCI Affinity Weigher. Weigh hosts by their PCI availability.
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Prefer hosts with PCI devices for instances with PCI requirements and vice
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versa. Configure the importance of this affinitization using the
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'pci_weight_multiplier' option.
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"""
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import nova.conf
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from nova.scheduler import weights
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CONF = nova.conf.CONF
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# An arbitrary value used to ensure PCI-requesting instances are stacked rather
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# than spread on hosts with PCI devices. The actual value of this filter is in
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# the scarcity case, where there are very few PCI devices left in the cloud and
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# we want to preserve the ones that do exist. To this end, we don't really mind
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# if a host with 2000 PCI devices is weighted the same as one with 500 devices,
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# as there's clearly no shortage there.
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MAX_DEVS = 100
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class PCIWeigher(weights.BaseHostWeigher):
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def weight_multiplier(self):
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"""Override the weight multiplier."""
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return CONF.filter_scheduler.pci_weight_multiplier
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def _weigh_object(self, host_state, request_spec):
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"""Higher weights win. We want to keep PCI hosts free unless needed.
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Prefer hosts with the least number of PCI devices. If the instance
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requests PCI devices, this will ensure a stacking behavior and reserve
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as many totally free PCI hosts as possible. If PCI devices are not
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requested, this will ensure hosts with PCI devices are avoided
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completely, if possible.
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"""
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pools = host_state.pci_stats.pools if host_state.pci_stats else []
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free = sum(pool['count'] for pool in pools) or 0
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# reverse the "has PCI" values. For instances *without* PCI device
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# requests, this ensures we avoid the hosts with the most free PCI
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# devices. For the instances *with* PCI devices requests, this helps to
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# prevent fragmentation. If we didn't do this, hosts with the most PCI
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# devices would be weighted highest and would be used first which would
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# prevent instances requesting a larger number of PCI devices from
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# launching successfully.
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weight = MAX_DEVS - min(free, MAX_DEVS - 1)
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return weight
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