func takeByTopology()

in pkg/scheduler/plugins/numaaware/provider/cpumanager/cpu_assignment.go [149:203]
43 lines of code
14 McCabe index (conditional complexity)

func takeByTopology(topo *topology.CPUTopology, availableCPUs cpuset.CPUSet, numCPUs int) (cpuset.CPUSet, error) {
	acc := newCPUAccumulator(topo, availableCPUs, numCPUs)
	if acc.isSatisfied() {
		return acc.result, nil
	}
	if acc.isFailed() {
		return cpuset.NewCPUSet(), fmt.Errorf("not enough cpus available to satisfy request")
	}

	// Algorithm: topology-aware best-fit
	// 1. Acquire whole sockets, if available and the container requires at
	//    least a socket's-worth of CPUs.
	if acc.needs(acc.topo.CPUsPerSocket()) {
		for _, s := range acc.freeSockets() {
			klog.V(4).Infof("[cpumanager] takeByTopology: claiming socket [%d]", s)
			acc.take(acc.details.CPUsInSockets(s))
			if acc.isSatisfied() {
				return acc.result, nil
			}
			if !acc.needs(acc.topo.CPUsPerSocket()) {
				break
			}
		}
	}

	// 2. Acquire whole cores, if available and the container requires at least
	//    a core's-worth of CPUs.
	if acc.needs(acc.topo.CPUsPerCore()) {
		for _, c := range acc.freeCores() {
			klog.V(4).Infof("[cpumanager] takeByTopology: claiming core [%d]", c)
			acc.take(acc.details.CPUsInCores(c))
			if acc.isSatisfied() {
				return acc.result, nil
			}
			if !acc.needs(acc.topo.CPUsPerCore()) {
				break
			}
		}
	}

	// 3. Acquire single threads, preferring to fill partially-allocated cores
	//    on the same sockets as the whole cores we have already taken in this
	//    allocation.
	for _, c := range acc.freeCPUs() {
		klog.V(4).Infof("[cpumanager] takeByTopology: claiming CPU [%d]", c)
		if acc.needs(1) {
			acc.take(cpuset.NewCPUSet(c))
		}
		if acc.isSatisfied() {
			return acc.result, nil
		}
	}

	return cpuset.NewCPUSet(), fmt.Errorf("failed to allocate cpus")
}