261e61f8ee
Profiling showed the MRU inventory handling was taking 5% of the total block handling time. Upon inspection this is because the original implementation was extremely inefficient using iteration to find the oldest node for eviction. This commit reworks it to use a map and list in order to achieve close to O(1) performance for lookups, insertion, and eviction. The following benchmark results show the difference: Before: BenchmarkMruInventoryList 100 1069168 ns/op After: BenchmarkMruInventoryList 10000000 152 ns/op Closes #21
97 lines
2.7 KiB
Go
97 lines
2.7 KiB
Go
// Copyright (c) 2013 Conformal Systems LLC.
|
|
// Use of this source code is governed by an ISC
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package main
|
|
|
|
import (
|
|
"container/list"
|
|
"fmt"
|
|
"github.com/conformal/btcwire"
|
|
)
|
|
|
|
// MruInventoryMap provides a map that is limited to a maximum number of items
|
|
// with eviction for the oldest entry when the limit is exceeded.
|
|
type MruInventoryMap struct {
|
|
invMap map[btcwire.InvVect]*list.Element // nearly O(1) lookups
|
|
invList *list.List // O(1) insert, update, delete
|
|
limit uint
|
|
}
|
|
|
|
// String returns the map as a human-readable string.
|
|
func (m MruInventoryMap) String() string {
|
|
return fmt.Sprintf("<%d>%v", m.limit, m.invMap)
|
|
}
|
|
|
|
// Exists returns whether or not the passed inventory item is in the map.
|
|
func (m *MruInventoryMap) Exists(iv *btcwire.InvVect) bool {
|
|
if _, exists := m.invMap[*iv]; exists {
|
|
return true
|
|
}
|
|
return false
|
|
}
|
|
|
|
// Add adds the passed inventory to the map and handles eviction of the oldest
|
|
// item if adding the new item would exceed the max limit.
|
|
func (m *MruInventoryMap) Add(iv *btcwire.InvVect) {
|
|
// When the limit is zero, nothing can be added to the map, so just
|
|
// return.
|
|
if m.limit == 0 {
|
|
return
|
|
}
|
|
|
|
// When the entry already exists move it to the front of the list
|
|
// thereby marking it most recently used.
|
|
if node, exists := m.invMap[*iv]; exists {
|
|
m.invList.MoveToFront(node)
|
|
return
|
|
}
|
|
|
|
// Evict the least recently used entry (back of the list) if the the new
|
|
// entry would exceed the size limit for the map. Also reuse the list
|
|
// node so a new one doesn't have to be allocated.
|
|
if uint(len(m.invMap))+1 > m.limit {
|
|
node := m.invList.Back()
|
|
lru, ok := node.Value.(*btcwire.InvVect)
|
|
if !ok {
|
|
return
|
|
}
|
|
|
|
// Evict least recently used item.
|
|
delete(m.invMap, *lru)
|
|
|
|
// Reuse the list node of the item that was just evicted for the
|
|
// new item.
|
|
node.Value = iv
|
|
m.invList.MoveToFront(node)
|
|
m.invMap[*iv] = node
|
|
return
|
|
}
|
|
|
|
// The limit hasn't been reached yet, so just add the new item.
|
|
node := m.invList.PushFront(iv)
|
|
m.invMap[*iv] = node
|
|
return
|
|
}
|
|
|
|
// Delete deletes the passed inventory item from the map (if it exists).
|
|
func (m *MruInventoryMap) Delete(iv *btcwire.InvVect) {
|
|
if node, exists := m.invMap[*iv]; exists {
|
|
m.invList.Remove(node)
|
|
delete(m.invMap, *iv)
|
|
}
|
|
}
|
|
|
|
// NewMruInventoryMap returns a new inventory map that is limited to the number
|
|
// of entries specified by limit. When the number of entries exceeds the limit,
|
|
// the oldest (least recently used) entry will be removed to make room for the
|
|
// new entry..
|
|
func NewMruInventoryMap(limit uint) *MruInventoryMap {
|
|
m := MruInventoryMap{
|
|
invMap: make(map[btcwire.InvVect]*list.Element),
|
|
invList: list.New(),
|
|
limit: limit,
|
|
}
|
|
return &m
|
|
}
|