syncthing/lib/model/deviceactivity.go

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// Copyright (C) 2014 The Syncthing Authors.
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at http://mozilla.org/MPL/2.0/.
package model
import (
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"github.com/syncthing/syncthing/lib/protocol"
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"github.com/syncthing/syncthing/lib/sync"
)
// deviceActivity tracks the number of outstanding requests per device and can
// answer which device is least busy. It is safe for use from multiple
// goroutines.
type deviceActivity struct {
act map[protocol.DeviceID]int
mut sync.Mutex
}
func newDeviceActivity() *deviceActivity {
return &deviceActivity{
act: make(map[protocol.DeviceID]int),
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mut: sync.NewMutex(),
}
}
func (m *deviceActivity) leastBusy(availability []protocol.DeviceID) protocol.DeviceID {
m.mut.Lock()
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low := 2<<30 - 1
var selected protocol.DeviceID
for _, device := range availability {
if usage := m.act[device]; usage < low {
low = usage
selected = device
}
}
m.mut.Unlock()
return selected
}
func (m *deviceActivity) using(device protocol.DeviceID) {
m.mut.Lock()
m.act[device]++
m.mut.Unlock()
}
func (m *deviceActivity) done(device protocol.DeviceID) {
m.mut.Lock()
m.act[device]--
m.mut.Unlock()
}