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coins: add Sync() method to allow flush without cacheCoins drop

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In certain circumstances, we may want to flush to disk without
emptying `cacheCoins`, which affects performance. UTXO snapshot
activation is one such case.

This method is currently unused and this commit does not
change any behavior.

Incorporates feedback from John Newbery.

Co-authored-by: Suhas Daftuar <sdaftuar@gmail.com>
This commit is contained in:
James O'Beirne
2019-12-03 13:25:35 -05:00
committed by James O'Beirne
parent c0b6c40bb0
commit 79cedc36af
5 changed files with 59 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

47
src/coins.cpp
View File

@@ -13,7 +13,7 @@
bool CCoinsView::GetCoin(const COutPoint &outpoint, Coin &coin) const { return false; }
uint256 CCoinsView::GetBestBlock() const { return uint256(); }
std::vector<uint256> CCoinsView::GetHeadBlocks() const { return std::vector<uint256>(); }
bool CCoinsView::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) { return false; }
bool CCoinsView::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock, bool erase) { return false; }
std::unique_ptr<CCoinsViewCursor> CCoinsView::Cursor() const { return nullptr; }
bool CCoinsView::HaveCoin(const COutPoint &outpoint) const
@@ -28,7 +28,7 @@ bool CCoinsViewBacked::HaveCoin(const COutPoint &outpoint) const { return base->
uint256 CCoinsViewBacked::GetBestBlock() const { return base->GetBestBlock(); }
std::vector<uint256> CCoinsViewBacked::GetHeadBlocks() const { return base->GetHeadBlocks(); }
void CCoinsViewBacked::SetBackend(CCoinsView &viewIn) { base = &viewIn; }
bool CCoinsViewBacked::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) { return base->BatchWrite(mapCoins, hashBlock); }
bool CCoinsViewBacked::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock, bool erase) { return base->BatchWrite(mapCoins, hashBlock, erase); }
std::unique_ptr<CCoinsViewCursor> CCoinsViewBacked::Cursor() const { return base->Cursor(); }
size_t CCoinsViewBacked::EstimateSize() const { return base->EstimateSize(); }
@@ -176,8 +176,10 @@ void CCoinsViewCache::SetBestBlock(const uint256 &hashBlockIn) {
hashBlock = hashBlockIn;
}
bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn) {
for (CCoinsMap::iterator it = mapCoins.begin(); it != mapCoins.end(); it = mapCoins.erase(it)) {
bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn, bool erase) {
for (CCoinsMap::iterator it = mapCoins.begin();
it != mapCoins.end();
it = erase ? mapCoins.erase(it) : std::next(it)) {
// Ignore non-dirty entries (optimization).
if (!(it->second.flags & CCoinsCacheEntry::DIRTY)) {
continue;
@@ -190,7 +192,14 @@ bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn
// Create the coin in the parent cache, move the data up
// and mark it as dirty.
CCoinsCacheEntry& entry = cacheCoins[it->first];
entry.coin = std::move(it->second.coin);
if (erase) {
// The `move` call here is purely an optimization; we rely on the
// `mapCoins.erase` call in the `for` expression to actually remove
// the entry from the child map.
entry.coin = std::move(it->second.coin);
} else {
entry.coin = it->second.coin;
}
cachedCoinsUsage += entry.coin.DynamicMemoryUsage();
entry.flags = CCoinsCacheEntry::DIRTY;
// We can mark it FRESH in the parent if it was FRESH in the child
@@ -218,7 +227,14 @@ bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn
} else {
// A normal modification.
cachedCoinsUsage -= itUs->second.coin.DynamicMemoryUsage();
itUs->second.coin = std::move(it->second.coin);
if (erase) {
// The `move` call here is purely an optimization; we rely on the
// `mapCoins.erase` call in the `for` expression to actually remove
// the entry from the child map.
itUs->second.coin = std::move(it->second.coin);
} else {
itUs->second.coin = it->second.coin;
}
cachedCoinsUsage += itUs->second.coin.DynamicMemoryUsage();
itUs->second.flags |= CCoinsCacheEntry::DIRTY;
// NOTE: It isn't safe to mark the coin as FRESH in the parent
@@ -233,12 +249,29 @@ bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn
}
bool CCoinsViewCache::Flush() {
bool fOk = base->BatchWrite(cacheCoins, hashBlock);
bool fOk = base->BatchWrite(cacheCoins, hashBlock, /*erase=*/ true);
cacheCoins.clear();
cachedCoinsUsage = 0;
return fOk;
}
bool CCoinsViewCache::Sync()
{
bool fOk = base->BatchWrite(cacheCoins, hashBlock, /*erase=*/ false);
// Instead of clearing `cacheCoins` as we would in Flush(), just clear the
// FRESH/DIRTY flags of any coin that isn't spent.
for (auto it = cacheCoins.begin(); it != cacheCoins.end(); ) {
if (it->second.coin.IsSpent()) {
cachedCoinsUsage -= it->second.coin.DynamicMemoryUsage();
it = cacheCoins.erase(it);
} else {
it->second.flags = 0;
++it;
}
}
return fOk;
}
void CCoinsViewCache::Uncache(const COutPoint& hash)
{
CCoinsMap::iterator it = cacheCoins.find(hash);

20
src/coins.h
View File

@@ -176,7 +176,7 @@ public:
//! Do a bulk modification (multiple Coin changes + BestBlock change).
//! The passed mapCoins can be modified.
virtual bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
virtual bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock, bool erase = true);
//! Get a cursor to iterate over the whole state
virtual std::unique_ptr<CCoinsViewCursor> Cursor() const;
@@ -202,7 +202,7 @@ public:
uint256 GetBestBlock() const override;
std::vector<uint256> GetHeadBlocks() const override;
void SetBackend(CCoinsView &viewIn);
bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock, bool erase = true) override;
std::unique_ptr<CCoinsViewCursor> Cursor() const override;
size_t EstimateSize() const override;
};
@@ -235,7 +235,7 @@ public:
bool HaveCoin(const COutPoint &outpoint) const override;
uint256 GetBestBlock() const override;
void SetBestBlock(const uint256 &hashBlock);
bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock, bool erase = true) override;
std::unique_ptr<CCoinsViewCursor> Cursor() const override {
throw std::logic_error("CCoinsViewCache cursor iteration not supported.");
}
@@ -282,12 +282,22 @@ public:
bool SpendCoin(const COutPoint &outpoint, Coin* moveto = nullptr);
/**
* Push the modifications applied to this cache to its base.
* Failure to call this method before destruction will cause the changes to be forgotten.
* Push the modifications applied to this cache to its base and wipe local state.
* Failure to call this method or Sync() before destruction will cause the changes
* to be forgotten.
* If false is returned, the state of this cache (and its backing view) will be undefined.
*/
bool Flush();
/**
* Push the modifications applied to this cache to its base while retaining
* the contents of this cache (except for spent coins, which we erase).
* Failure to call this method or Flush() before destruction will cause the changes
* to be forgotten.
* If false is returned, the state of this cache (and its backing view) will be undefined.
*/
bool Sync();
/**
* Removes the UTXO with the given outpoint from the cache, if it is
* not modified.

2
src/test/coins_tests.cpp
View File

@@ -53,7 +53,7 @@ public:
uint256 GetBestBlock() const override { return hashBestBlock_; }
bool BatchWrite(CCoinsMap& mapCoins, const uint256& hashBlock) override
bool BatchWrite(CCoinsMap& mapCoins, const uint256& hashBlock, bool erase = true) override
{
for (CCoinsMap::iterator it = mapCoins.begin(); it != mapCoins.end(); ) {
if (it->second.flags & CCoinsCacheEntry::DIRTY) {

5
src/txdb.cpp
View File

@@ -111,7 +111,7 @@ std::vector<uint256> CCoinsViewDB::GetHeadBlocks() const {
return vhashHeadBlocks;
}
bool CCoinsViewDB::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) {
bool CCoinsViewDB::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock, bool erase) {
CDBBatch batch(*m_db);
size_t count = 0;
size_t changed = 0;
@@ -146,8 +146,7 @@ bool CCoinsViewDB::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) {
changed++;
}
count++;
CCoinsMap::iterator itOld = it++;
mapCoins.erase(itOld);
it = erase ? mapCoins.erase(it) : std::next(it);
if (batch.SizeEstimate() > batch_size) {
LogPrint(BCLog::COINDB, "Writing partial batch of %.2f MiB\n", batch.SizeEstimate() * (1.0 / 1048576.0));
m_db->WriteBatch(batch);

2
src/txdb.h
View File

@@ -62,7 +62,7 @@ public:
bool HaveCoin(const COutPoint &outpoint) const override;
uint256 GetBestBlock() const override;
std::vector<uint256> GetHeadBlocks() const override;
bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock, bool erase = true) override;
std::unique_ptr<CCoinsViewCursor> Cursor() const override;
//! Whether an unsupported database format is used.