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https://github.com/optim-enterprises-bv/kubernetes.git
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79 lines
2.6 KiB
Go
79 lines
2.6 KiB
Go
/*
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Copyright 2020 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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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,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package parallelize
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import (
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"context"
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"math"
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"k8s.io/client-go/util/workqueue"
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"k8s.io/kubernetes/pkg/scheduler/metrics"
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)
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// DefaultParallelism is the default parallelism used in scheduler.
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const DefaultParallelism int = 16
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// Parallelizer holds the parallelism for scheduler.
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type Parallelizer struct {
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parallelism int
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}
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// NewParallelizer returns an object holding the parallelism.
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func NewParallelizer(p int) Parallelizer {
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return Parallelizer{parallelism: p}
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}
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// chunkSizeFor returns a chunk size for the given number of items to use for
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// parallel work. The size aims to produce good CPU utilization.
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// returns max(1, min(sqrt(n), n/Parallelism))
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func chunkSizeFor(n, parallelism int) int {
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s := int(math.Sqrt(float64(n)))
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if r := n/parallelism + 1; s > r {
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s = r
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} else if s < 1 {
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s = 1
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}
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return s
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}
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// numWorkersForChunkSize returns number of workers (goroutines)
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// that will be created in workqueue.ParallelizeUntil
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// for given parallelism, pieces and chunkSize values.
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func numWorkersForChunkSize(parallelism, pieces, chunkSize int) int {
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chunks := (pieces + chunkSize - 1) / chunkSize
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if chunks < parallelism {
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return chunks
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}
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return parallelism
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}
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// Until is a wrapper around workqueue.ParallelizeUntil to use in scheduling algorithms.
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// A given operation will be a label that is recorded in the goroutine metric.
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func (p Parallelizer) Until(ctx context.Context, pieces int, doWorkPiece workqueue.DoWorkPieceFunc, operation string) {
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chunkSize := chunkSizeFor(pieces, p.parallelism)
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workers := numWorkersForChunkSize(p.parallelism, pieces, chunkSize)
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goroutinesMetric := metrics.Goroutines.WithLabelValues(operation)
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// Calling single Add with workers' count is more efficient than calling Inc or Dec per each work piece.
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// This approach improves performance of some plugins (affinity, topology spreading) as well as preemption.
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goroutinesMetric.Add(float64(workers))
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defer goroutinesMetric.Add(float64(-workers))
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workqueue.ParallelizeUntil(ctx, p.parallelism, pieces, doWorkPiece, workqueue.WithChunkSize(chunkSize))
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}
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