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coins: Keep track of number of dirty entries in `CCoinsViewCache` 

Adds `m_dirty_count` member to track the running count of dirty cache entries as follows:
* Incremented when entries are marked dirty via `CCoinsCacheEntry::SetDirty`
* Decremented when dirty entries are removed or cleaned
* Passed through `CoinsViewCacheCursor` and updated during iteration
* Validated in `SanityCheck()` by recomputing from scratch

The dirty count is needed because after non-wiping flushes (introduced in #28280 and #28233), the percentage of dirty entries in the cache may be far below 100%. Using total cache size for flush warnings and disk space checks is therefore misleading.

Updates all test code to properly initialize and maintain the dirty count.

Co-authored-by: l0rinc <pap.lorinc@gmail.com>
This commit is contained in:
Pieter Wuille 2025-01-21 14:02:10 -05:00 committed by Lőrinc
parent 3dc15c9607
commit 801e7bb2d2
4 changed files with 44 additions and 11 deletions
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26
src/coins.cpp
View File

@ -96,10 +96,12 @@ void CCoinsViewCache::AddCoin(const COutPoint &outpoint, Coin&& coin, bool possi
fresh = !it->second.IsDirty();
}
if (!inserted) {
m_dirty_count -= it->second.IsDirty();
cachedCoinsUsage -= it->second.coin.DynamicMemoryUsage();
}
it->second.coin = std::move(coin);
CCoinsCacheEntry::SetDirty(*it, m_sentinel);
++m_dirty_count;
if (fresh) CCoinsCacheEntry::SetFresh(*it, m_sentinel);
cachedCoinsUsage += it->second.coin.DynamicMemoryUsage();
TRACEPOINT(utxocache, add,
@ -115,6 +117,7 @@ void CCoinsViewCache::EmplaceCoinInternalDANGER(COutPoint&& outpoint, Coin&& coi
auto [it, inserted] = cacheCoins.try_emplace(std::move(outpoint), std::move(coin));
if (inserted) {
CCoinsCacheEntry::SetDirty(*it, m_sentinel);
++m_dirty_count;
cachedCoinsUsage += mem_usage;
}
}
@ -133,6 +136,7 @@ void AddCoins(CCoinsViewCache& cache, const CTransaction &tx, int nHeight, bool
bool CCoinsViewCache::SpendCoin(const COutPoint &outpoint, Coin* moveout) {
CCoinsMap::iterator it = FetchCoin(outpoint);
if (it == cacheCoins.end()) return false;
m_dirty_count -= it->second.IsDirty();
cachedCoinsUsage -= it->second.coin.DynamicMemoryUsage();
TRACEPOINT(utxocache, spent,
outpoint.hash.data(),
@ -147,6 +151,7 @@ bool CCoinsViewCache::SpendCoin(const COutPoint &outpoint, Coin* moveout) {
cacheCoins.erase(it);
} else {
CCoinsCacheEntry::SetDirty(*it, m_sentinel);
++m_dirty_count;
it->second.coin.Clear();
}
return true;
@ -205,8 +210,9 @@ bool CCoinsViewCache::BatchWrite(CoinsViewCacheCursor& cursor, const uint256 &ha
} else {
entry.coin = it->second.coin;
}
cachedCoinsUsage += entry.coin.DynamicMemoryUsage();
CCoinsCacheEntry::SetDirty(*itUs, m_sentinel);
++m_dirty_count;
cachedCoinsUsage += entry.coin.DynamicMemoryUsage();
// We can mark it FRESH in the parent if it was FRESH in the child
// Otherwise it might have just been flushed from the parent's cache
// and already exist in the grandparent
@ -225,6 +231,7 @@ bool CCoinsViewCache::BatchWrite(CoinsViewCacheCursor& cursor, const uint256 &ha
if (itUs->second.IsFresh() && it->second.coin.IsSpent()) {
// The grandparent cache does not have an entry, and the coin
// has been spent. We can just delete it from the parent cache.
m_dirty_count -= itUs->second.IsDirty();
cachedCoinsUsage -= itUs->second.coin.DynamicMemoryUsage();
cacheCoins.erase(itUs);
} else {
@ -238,7 +245,10 @@ bool CCoinsViewCache::BatchWrite(CoinsViewCacheCursor& cursor, const uint256 &ha
itUs->second.coin = it->second.coin;
}
cachedCoinsUsage += itUs->second.coin.DynamicMemoryUsage();
CCoinsCacheEntry::SetDirty(*itUs, m_sentinel);
if (!itUs->second.IsDirty()) {
CCoinsCacheEntry::SetDirty(*itUs, m_sentinel);
++m_dirty_count;
}
// NOTE: It isn't safe to mark the coin as FRESH in the parent
// cache. If it already existed and was spent in the parent
// cache then marking it FRESH would prevent that spentness
@ -251,21 +261,23 @@ bool CCoinsViewCache::BatchWrite(CoinsViewCacheCursor& cursor, const uint256 &ha
}
bool CCoinsViewCache::Flush() {
auto cursor{CoinsViewCacheCursor(cachedCoinsUsage, m_sentinel, cacheCoins, /*will_erase=*/true)};
auto cursor{CoinsViewCacheCursor(cachedCoinsUsage, m_dirty_count, m_sentinel, cacheCoins, /*will_erase=*/true)};
bool fOk = base->BatchWrite(cursor, hashBlock);
if (fOk) {
cacheCoins.clear();
ReallocateCache();
}
cachedCoinsUsage = 0;
m_dirty_count = 0;
return fOk;
}
bool CCoinsViewCache::Sync()
{
auto cursor{CoinsViewCacheCursor(cachedCoinsUsage, m_sentinel, cacheCoins, /*will_erase=*/false)};
auto cursor{CoinsViewCacheCursor(cachedCoinsUsage, m_dirty_count, m_sentinel, cacheCoins, /*will_erase=*/false)};
bool fOk = base->BatchWrite(cursor, hashBlock);
if (fOk) {
Assume(m_dirty_count == 0);
if (m_sentinel.second.Next() != &m_sentinel) {
/* BatchWrite must clear flags of all entries */
throw std::logic_error("Not all unspent flagged entries were cleared");
@ -309,6 +321,7 @@ void CCoinsViewCache::ReallocateCache()
{
// Cache should be empty when we're calling this.
assert(cacheCoins.size() == 0);
Assume(m_dirty_count == 0);
cacheCoins.~CCoinsMap();
m_cache_coins_memory_resource.~CCoinsMapMemoryResource();
::new (&m_cache_coins_memory_resource) CCoinsMapMemoryResource{};
@ -319,6 +332,7 @@ void CCoinsViewCache::SanityCheck() const
{
size_t recomputed_usage = 0;
size_t count_flagged = 0;
size_t dirty_count = 0;
for (const auto& [_, entry] : cacheCoins) {
unsigned attr = 0;
if (entry.IsDirty()) attr |= 1;
@ -330,6 +344,9 @@ void CCoinsViewCache::SanityCheck() const
// Recompute cachedCoinsUsage.
recomputed_usage += entry.coin.DynamicMemoryUsage();
// Recompute dirty_count.
dirty_count += entry.IsDirty();
// Count the number of entries we expect in the linked list.
if (entry.IsDirty() || entry.IsFresh()) ++count_flagged;
}
@ -346,6 +363,7 @@ void CCoinsViewCache::SanityCheck() const
}
assert(count_linked == count_flagged);
assert(recomputed_usage == cachedCoinsUsage);
assert(dirty_count == m_dirty_count);
}
static const size_t MIN_TRANSACTION_OUTPUT_WEIGHT = WITNESS_SCALE_FACTOR * ::GetSerializeSize(CTxOut());

16
src/coins.h
View File

@ -272,10 +272,11 @@ struct CoinsViewCacheCursor
//! Calling CCoinsMap::clear() afterwards is faster because a CoinsCachePair cannot be coerced back into a
//! CCoinsMap::iterator to be erased, and must therefore be looked up again by key in the CCoinsMap before being erased.
CoinsViewCacheCursor(size_t& usage LIFETIMEBOUND,
CoinsCachePair& sentinel LIFETIMEBOUND,
CCoinsMap& map LIFETIMEBOUND,
bool will_erase) noexcept
: m_usage(usage), m_sentinel(sentinel), m_map(map), m_will_erase(will_erase) {}
size_t& dirty_count LIFETIMEBOUND,
CoinsCachePair& sentinel LIFETIMEBOUND,
CCoinsMap& map LIFETIMEBOUND,
bool will_erase) noexcept
: m_usage(usage), m_dirty_count(dirty_count), m_sentinel(sentinel), m_map(map), m_will_erase(will_erase) {}
inline CoinsCachePair* Begin() const noexcept { return m_sentinel.second.Next(); }
inline CoinsCachePair* End() const noexcept { return &m_sentinel; }
@ -284,6 +285,7 @@ struct CoinsViewCacheCursor
inline CoinsCachePair* NextAndMaybeErase(CoinsCachePair& current) noexcept
{
const auto next_entry{current.second.Next()};
m_dirty_count -= current.second.IsDirty();
// If we are not going to erase the cache, we must still erase spent entries.
// Otherwise, clear the state of the entry.
if (!m_will_erase) {
@ -300,6 +302,7 @@ struct CoinsViewCacheCursor
inline bool WillErase(CoinsCachePair& current) const noexcept { return m_will_erase || current.second.coin.IsSpent(); }
private:
size_t& m_usage;
size_t& m_dirty_count;
CoinsCachePair& m_sentinel;
CCoinsMap& m_map;
bool m_will_erase;
@ -377,6 +380,8 @@ protected:
/* Cached dynamic memory usage for the inner Coin objects. */
mutable size_t cachedCoinsUsage{0};
/* Running count of dirty Coin cache entries. */
mutable size_t m_dirty_count{0};
public:
CCoinsViewCache(CCoinsView *baseIn, bool deterministic = false);
@ -463,6 +468,9 @@ public:
//! Calculate the size of the cache (in number of transaction outputs)
unsigned int GetCacheSize() const;
//! Calculate the number of dirty cache entries (transaction outputs)
size_t GetDirtyCount() const noexcept { return m_dirty_count; }
//! Calculate the size of the cache (in bytes)
size_t DynamicMemoryUsage() const;

9
src/test/coins_tests.cpp
View File

@ -100,6 +100,7 @@ public:
CCoinsMap& map() const { return cacheCoins; }
CoinsCachePair& sentinel() const { return m_sentinel; }
size_t& usage() const { return cachedCoinsUsage; }
size_t& dirty() const { return m_dirty_count; }
};
} // namespace
@ -666,7 +667,8 @@ static void WriteCoinsViewEntry(CCoinsView& view, const MaybeCoin& cache_coin)
CCoinsMapMemoryResource resource;
CCoinsMap map{0, CCoinsMap::hasher{}, CCoinsMap::key_equal{}, &resource};
auto usage{cache_coin ? InsertCoinsMapEntry(map, sentinel, *cache_coin) : 0};
auto cursor{CoinsViewCacheCursor(usage, sentinel, map, /*will_erase=*/true)};
size_t dirty_count{cache_coin && cache_coin->IsDirty() ? 1U : 0U};
auto cursor{CoinsViewCacheCursor(usage, dirty_count, sentinel, map, /*will_erase=*/true)};
BOOST_CHECK(view.BatchWrite(cursor, {}));
}
@ -677,7 +679,10 @@ public:
{
auto base_cache_coin{base_value == ABSENT ? MISSING : CoinEntry{base_value, CoinEntry::State::DIRTY}};
WriteCoinsViewEntry(base, base_cache_coin);
if (cache_coin) cache.usage() += InsertCoinsMapEntry(cache.map(), cache.sentinel(), *cache_coin);
if (cache_coin) {
cache.usage() += InsertCoinsMapEntry(cache.map(), cache.sentinel(), *cache_coin);
cache.dirty() += cache_coin->IsDirty();
}
}
CCoinsView root;

4
src/test/fuzz/coins_view.cpp
View File

@ -126,6 +126,7 @@ void TestCoinsView(FuzzedDataProvider& fuzzed_data_provider, CCoinsView& backend
CoinsCachePair sentinel{};
sentinel.second.SelfRef(sentinel);
size_t usage{0};
size_t dirty_count{0};
CCoinsMapMemoryResource resource;
CCoinsMap coins_map{0, SaltedOutpointHasher{/*deterministic=*/true}, CCoinsMap::key_equal{}, &resource};
LIMITED_WHILE(good_data && fuzzed_data_provider.ConsumeBool(), 10'000)
@ -147,10 +148,11 @@ void TestCoinsView(FuzzedDataProvider& fuzzed_data_provider, CCoinsView& backend
if (dirty) CCoinsCacheEntry::SetDirty(*it, sentinel);
if (fresh) CCoinsCacheEntry::SetFresh(*it, sentinel);
usage += it->second.coin.DynamicMemoryUsage();
dirty_count += dirty;
}
bool expected_code_path = false;
try {
auto cursor{CoinsViewCacheCursor(usage, sentinel, coins_map, /*will_erase=*/true)};
auto cursor{CoinsViewCacheCursor(usage, dirty_count, sentinel, coins_map, /*will_erase=*/true)};
uint256 best_block{coins_view_cache.GetBestBlock()};
if (fuzzed_data_provider.ConsumeBool()) best_block = ConsumeUInt256(fuzzed_data_provider);
// Set best block hash to non-null to satisfy the assertion in CCoinsViewDB::BatchWrite().