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Do not keep fully spent but unwritten CCoins entries cached.

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Instead of storing CCoins entries directly in CCoinsMap, store a CCoinsCacheEntry
which additionally keeps track of whether a particular entry is:
* dirty: potentially different from its parent view.
* fresh: the parent view is known to not have a non-pruned version.

This allows us to skip non-dirty cache entries when pushing batches of changes up,
and to remove CCoins entries about transactions that are fully spent before the
parent cache learns about them.
pull/196/head
Pieter Wuille 10 years ago
parent c9d1a81ce7
commit 058b08c147
4 changed files with 88 additions and 31 deletions
Show Stats Download Patch File Download Diff File

83
src/coins.cpp
Unescape View File

@ -71,18 +71,6 @@ CCoinsKeyHasher::CCoinsKeyHasher() : salt(GetRandHash()) {}
CCoinsViewCache::CCoinsViewCache(CCoinsView &baseIn, bool fDummy) : CCoinsViewBacked(baseIn), hasModifier(false), hashBlock(0) { }
bool CCoinsViewCache::GetCoins(const uint256 &txid, CCoins &coins) const {
if (cacheCoins.count(txid)) {
coins = cacheCoins[txid];
return true;
}
if (base->GetCoins(txid, coins)) {
cacheCoins[txid] = coins;
return true;
}
return false;
}
CCoinsViewCache::~CCoinsViewCache()
{
assert(!hasModifier);
@ -95,19 +83,41 @@ CCoinsMap::const_iterator CCoinsViewCache::FetchCoins(const uint256 &txid) const
CCoins tmp;
if (!base->GetCoins(txid, tmp))
return cacheCoins.end();
CCoinsMap::iterator ret = cacheCoins.insert(it, std::make_pair(txid, CCoins()));
tmp.swap(ret->second);
CCoinsMap::iterator ret = cacheCoins.insert(std::make_pair(txid, CCoinsCacheEntry())).first;
tmp.swap(ret->second.coins);
if (ret->second.coins.IsPruned()) {
// The parent only has an empty entry for this txid; we can consider our
// version as fresh.
ret->second.flags = CCoinsCacheEntry::FRESH;
}
return ret;
}
bool CCoinsViewCache::GetCoins(const uint256 &txid, CCoins &coins) const {
CCoinsMap::const_iterator it = FetchCoins(txid);
if (it != cacheCoins.end()) {
coins = it->second.coins;
return true;
}
return false;
}
CCoinsModifier CCoinsViewCache::ModifyCoins(const uint256 &txid) {
assert(!hasModifier);
hasModifier = true;
std::pair<CCoinsMap::iterator, bool> ret = cacheCoins.insert(std::make_pair(txid, CCoins()));
std::pair<CCoinsMap::iterator, bool> ret = cacheCoins.insert(std::make_pair(txid, CCoinsCacheEntry()));
if (ret.second) {
if (!base->GetCoins(txid, ret.first->second))
ret.first->second.Clear();
if (!base->GetCoins(txid, ret.first->second.coins)) {
// The parent view does not have this entry; mark it as fresh.
ret.first->second.coins.Clear();
ret.first->second.flags = CCoinsCacheEntry::FRESH;
} else if (ret.first->second.coins.IsPruned()) {
// The parent view only has a pruned entry for this; mark it as fresh.
ret.first->second.flags = CCoinsCacheEntry::FRESH;
}
}
// Assume that whenever ModifyCoins is called, the entry will be modified.
ret.first->second.flags |= CCoinsCacheEntry::DIRTY;
return CCoinsModifier(*this, ret.first);
}
@ -116,7 +126,7 @@ const CCoins* CCoinsViewCache::AccessCoins(const uint256 &txid) const {
if (it == cacheCoins.end()) {
return NULL;
} else {
return &it->second;
return &it->second.coins;
}
}
@ -126,7 +136,7 @@ bool CCoinsViewCache::HaveCoins(const uint256 &txid) const {
// as we only care about the case where an transaction was replaced entirely
// in a reorganization (which wipes vout entirely, as opposed to spending
// which just cleans individual outputs).
return (it != cacheCoins.end() && !it->second.vout.empty());
return (it != cacheCoins.end() && !it->second.coins.vout.empty());
}
uint256 CCoinsViewCache::GetBestBlock() const {
@ -142,7 +152,32 @@ void CCoinsViewCache::SetBestBlock(const uint256 &hashBlockIn) {
bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn) {
assert(!hasModifier);
for (CCoinsMap::iterator it = mapCoins.begin(); it != mapCoins.end();) {
cacheCoins[it->first].swap(it->second);
if (it->second.flags & CCoinsCacheEntry::DIRTY) { // Ignore non-dirty entries (optimization).
CCoinsMap::iterator itUs = cacheCoins.find(it->first);
if (itUs == cacheCoins.end()) {
if (!it->second.coins.IsPruned()) {
// The parent cache does not have an entry, while the child
// cache does have (a non-pruned) one. Move the data up, and
// mark it as fresh (if the grandparent did have it, we
// would have pulled it in at first GetCoins).
assert(it->second.flags & CCoinsCacheEntry::FRESH);
CCoinsCacheEntry& entry = cacheCoins[it->first];
entry.coins.swap(it->second.coins);
entry.flags = CCoinsCacheEntry::DIRTY | CCoinsCacheEntry::FRESH;
}
} else {
if ((itUs->second.flags & CCoinsCacheEntry::FRESH) && it->second.coins.IsPruned()) {
// The grandparent does not have an entry, and the child is
// modified and being pruned. This means we can just delete
// it from the parent.
cacheCoins.erase(itUs);
} else {
// A normal modification.
itUs->second.coins.swap(it->second.coins);
itUs->second.flags |= CCoinsCacheEntry::DIRTY;
}
}
}
CCoinsMap::iterator itOld = it++;
mapCoins.erase(itOld);
}
@ -212,8 +247,12 @@ double CCoinsViewCache::GetPriority(const CTransaction &tx, int nHeight) const
CCoinsModifier::CCoinsModifier(CCoinsViewCache& cache_, CCoinsMap::iterator it_) : cache(cache_), it(it_) {}
CCoinsModifier::~CCoinsModifier() {
CCoinsModifier::~CCoinsModifier()
{
assert(cache.hasModifier);
cache.hasModifier = false;
it->second.Cleanup();
it->second.coins.Cleanup();
if ((it->second.flags & CCoinsCacheEntry::FRESH) && it->second.coins.IsPruned()) {
cache.cacheCoins.erase(it);
}
}

19
src/coins.h
Unescape View File

@ -271,7 +271,20 @@ public:
}
};
typedef boost::unordered_map<uint256, CCoins, CCoinsKeyHasher> CCoinsMap;
struct CCoinsCacheEntry
{
CCoins coins; // The actual cached data.
unsigned char flags;
enum Flags {
DIRTY = (1 << 0), // This cache entry is potentially different from the version in the parent view.
FRESH = (1 << 1), // The parent view does not have this entry (or it is pruned).
};
CCoinsCacheEntry() : coins(), flags(0) {}
};
typedef boost::unordered_map<uint256, CCoinsCacheEntry, CCoinsKeyHasher> CCoinsMap;
struct CCoinsStats
{
@ -343,8 +356,8 @@ private:
CCoinsModifier(CCoinsViewCache& cache_, CCoinsMap::iterator it_);
public:
CCoins* operator->() { return &it->second; }
CCoins& operator*() { return it->second; }
CCoins* operator->() { return &it->second.coins; }
CCoins& operator*() { return it->second.coins; }
~CCoinsModifier();
friend class CCoinsViewCache;
};

4
src/main.cpp
Unescape View File

@ -1797,10 +1797,10 @@ void static UpdateTip(CBlockIndex *pindexNew) {
nTimeBestReceived = GetTime();
mempool.AddTransactionsUpdated(1);
LogPrintf("UpdateTip: new best=%s height=%d log2_work=%.8g tx=%lu date=%s progress=%f\n",
LogPrintf("UpdateTip: new best=%s height=%d log2_work=%.8g tx=%lu date=%s progress=%f cache=%u\n",
chainActive.Tip()->GetBlockHash().ToString(), chainActive.Height(), log(chainActive.Tip()->nChainWork.getdouble())/log(2.0), (unsigned long)chainActive.Tip()->nChainTx,
DateTimeStrFormat("%Y-%m-%d %H:%M:%S", chainActive.Tip()->GetBlockTime()),
Checkpoints::GuessVerificationProgress(chainActive.Tip()));
Checkpoints::GuessVerificationProgress(chainActive.Tip()), (unsigned int)pcoinsTip->GetCacheSize());
cvBlockChange.notify_all();

11
src/txdb.cpp
Unescape View File

@ -45,17 +45,22 @@ uint256 CCoinsViewDB::GetBestBlock() const {
}
bool CCoinsViewDB::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) {
LogPrint("coindb", "Committing %u changed transactions to coin database...\n", (unsigned int)mapCoins.size());
CLevelDBBatch batch;
size_t count = 0;
size_t changed = 0;
for (CCoinsMap::iterator it = mapCoins.begin(); it != mapCoins.end();) {
BatchWriteCoins(batch, it->first, it->second);
if (it->second.flags & CCoinsCacheEntry::DIRTY) {
BatchWriteCoins(batch, it->first, it->second.coins);
changed++;
}
count++;
CCoinsMap::iterator itOld = it++;
mapCoins.erase(itOld);
}
if (hashBlock != uint256(0))
BatchWriteHashBestChain(batch, hashBlock);
LogPrint("coindb", "Committing %u changed transactions (out of %u) to coin database...\n", (unsigned int)changed, (unsigned int)count);
return db.WriteBatch(batch);
}

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