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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.
This commit is contained in:
Pieter Wuille 2014-09-03 09:37:47 +02:00
parent c9d1a81ce7
commit 058b08c147
4 changed files with 88 additions and 31 deletions
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83
src/coins.cpp
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
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
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
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);
}