317 lines
6.7 KiB
Go
317 lines
6.7 KiB
Go
// Copyright 2016 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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// memory storage layer for the package blockhash
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package storage
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import (
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"sync"
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)
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const (
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memTreeLW = 2 // log2(subtree count) of the subtrees
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memTreeFLW = 14 // log2(subtree count) of the root layer
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dbForceUpdateAccessCnt = 1000
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defaultCacheCapacity = 5000
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)
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type MemStore struct {
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memtree *memTree
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entryCnt, capacity uint // stored entries
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accessCnt uint64 // access counter; oldest is thrown away when full
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dbAccessCnt uint64
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dbStore *DbStore
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lock sync.Mutex
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}
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/*
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a hash prefix subtree containing subtrees or one storage entry (but never both)
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- access[0] stores the smallest (oldest) access count value in this subtree
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- if it contains more subtrees and its subtree count is at least 4, access[1:2]
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stores the smallest access count in the first and second halves of subtrees
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(so that access[0] = min(access[1], access[2])
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- likewise, if subtree count is at least 8,
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access[1] = min(access[3], access[4])
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access[2] = min(access[5], access[6])
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(access[] is a binary tree inside the multi-bit leveled hash tree)
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*/
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func NewMemStore(d *DbStore, capacity uint) (m *MemStore) {
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m = &MemStore{}
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m.memtree = newMemTree(memTreeFLW, nil, 0)
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m.dbStore = d
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m.setCapacity(capacity)
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return
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}
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type memTree struct {
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subtree []*memTree
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parent *memTree
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parentIdx uint
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bits uint // log2(subtree count)
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width uint // subtree count
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entry *Chunk // if subtrees are present, entry should be nil
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lastDBaccess uint64
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access []uint64
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}
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func newMemTree(b uint, parent *memTree, pidx uint) (node *memTree) {
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node = new(memTree)
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node.bits = b
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node.width = 1 << uint(b)
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node.subtree = make([]*memTree, node.width)
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node.access = make([]uint64, node.width-1)
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node.parent = parent
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node.parentIdx = pidx
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if parent != nil {
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parent.subtree[pidx] = node
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}
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return node
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}
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func (node *memTree) updateAccess(a uint64) {
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aidx := uint(0)
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var aa uint64
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oa := node.access[0]
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for node.access[aidx] == oa {
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node.access[aidx] = a
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if aidx > 0 {
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aa = node.access[((aidx-1)^1)+1]
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aidx = (aidx - 1) >> 1
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} else {
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pidx := node.parentIdx
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node = node.parent
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if node == nil {
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return
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}
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nn := node.subtree[pidx^1]
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if nn != nil {
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aa = nn.access[0]
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} else {
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aa = 0
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}
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aidx = (node.width + pidx - 2) >> 1
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}
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if (aa != 0) && (aa < a) {
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a = aa
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}
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}
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}
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func (s *MemStore) setCapacity(c uint) {
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s.lock.Lock()
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defer s.lock.Unlock()
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for c < s.entryCnt {
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s.removeOldest()
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}
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s.capacity = c
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}
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func (s *MemStore) getEntryCnt() uint {
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return s.entryCnt
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}
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// entry (not its copy) is going to be in MemStore
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func (s *MemStore) Put(entry *Chunk) {
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if s.capacity == 0 {
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return
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}
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s.lock.Lock()
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defer s.lock.Unlock()
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if s.entryCnt >= s.capacity {
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s.removeOldest()
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}
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s.accessCnt++
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node := s.memtree
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bitpos := uint(0)
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for node.entry == nil {
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l := entry.Key.bits(bitpos, node.bits)
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st := node.subtree[l]
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if st == nil {
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st = newMemTree(memTreeLW, node, l)
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bitpos += node.bits
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node = st
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break
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}
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bitpos += node.bits
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node = st
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}
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if node.entry != nil {
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if node.entry.Key.isEqual(entry.Key) {
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node.updateAccess(s.accessCnt)
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if entry.SData == nil {
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entry.Size = node.entry.Size
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entry.SData = node.entry.SData
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}
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if entry.Req == nil {
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entry.Req = node.entry.Req
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}
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entry.C = node.entry.C
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node.entry = entry
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return
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}
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for node.entry != nil {
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l := node.entry.Key.bits(bitpos, node.bits)
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st := node.subtree[l]
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if st == nil {
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st = newMemTree(memTreeLW, node, l)
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}
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st.entry = node.entry
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node.entry = nil
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st.updateAccess(node.access[0])
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l = entry.Key.bits(bitpos, node.bits)
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st = node.subtree[l]
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if st == nil {
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st = newMemTree(memTreeLW, node, l)
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}
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bitpos += node.bits
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node = st
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}
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}
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node.entry = entry
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node.lastDBaccess = s.dbAccessCnt
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node.updateAccess(s.accessCnt)
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s.entryCnt++
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return
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}
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func (s *MemStore) Get(hash Key) (chunk *Chunk, err error) {
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s.lock.Lock()
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defer s.lock.Unlock()
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node := s.memtree
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bitpos := uint(0)
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for node.entry == nil {
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l := hash.bits(bitpos, node.bits)
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st := node.subtree[l]
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if st == nil {
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return nil, notFound
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}
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bitpos += node.bits
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node = st
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}
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if node.entry.Key.isEqual(hash) {
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s.accessCnt++
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node.updateAccess(s.accessCnt)
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chunk = node.entry
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if s.dbAccessCnt-node.lastDBaccess > dbForceUpdateAccessCnt {
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s.dbAccessCnt++
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node.lastDBaccess = s.dbAccessCnt
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if s.dbStore != nil {
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s.dbStore.updateAccessCnt(hash)
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}
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}
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} else {
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err = notFound
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}
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return
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}
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func (s *MemStore) removeOldest() {
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node := s.memtree
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for node.entry == nil {
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aidx := uint(0)
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av := node.access[aidx]
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for aidx < node.width/2-1 {
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if av == node.access[aidx*2+1] {
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node.access[aidx] = node.access[aidx*2+2]
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aidx = aidx*2 + 1
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} else if av == node.access[aidx*2+2] {
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node.access[aidx] = node.access[aidx*2+1]
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aidx = aidx*2 + 2
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} else {
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panic(nil)
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}
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}
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pidx := aidx*2 + 2 - node.width
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if (node.subtree[pidx] != nil) && (av == node.subtree[pidx].access[0]) {
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if node.subtree[pidx+1] != nil {
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node.access[aidx] = node.subtree[pidx+1].access[0]
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} else {
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node.access[aidx] = 0
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}
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} else if (node.subtree[pidx+1] != nil) && (av == node.subtree[pidx+1].access[0]) {
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if node.subtree[pidx] != nil {
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node.access[aidx] = node.subtree[pidx].access[0]
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} else {
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node.access[aidx] = 0
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}
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pidx++
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} else {
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panic(nil)
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}
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//fmt.Println(pidx)
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node = node.subtree[pidx]
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}
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if node.entry.dbStored != nil {
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<-node.entry.dbStored
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}
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if node.entry.SData != nil {
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node.entry = nil
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s.entryCnt--
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}
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node.access[0] = 0
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//---
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aidx := uint(0)
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for {
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aa := node.access[aidx]
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if aidx > 0 {
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aidx = (aidx - 1) >> 1
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} else {
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pidx := node.parentIdx
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node = node.parent
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if node == nil {
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return
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}
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aidx = (node.width + pidx - 2) >> 1
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}
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if (aa != 0) && ((aa < node.access[aidx]) || (node.access[aidx] == 0)) {
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node.access[aidx] = aa
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}
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}
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}
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