Merge 0fe4ba2a85 into b510893d00

Changes flush warnings to use the actual number of dirty entries being written rather than total cache size or memory usage:
* Moves warning from `FlushStateToDisk` to `CCoinsViewDB::BatchWrite` so it applies to both regular flushes and `AssumeUTXO` snapshot writes
* Changes threshold from `WARN_FLUSH_COINS_SIZE` (1 GiB) to `WARN_FLUSH_COINS_COUNT` (10M entries), approximately equivalent - this also helps with the confusion caused by UTXO size difference on-disk vs in-memory
* Moves benchmark logging to `BatchWrite` where the actual disk I/O occurs to make sure AssumeUTXO also warns
* Uses dirty count for disk space check (48 bytes per entry estimate)
* Removes redundant `changed` counter since `dirty_count` is now tracked

This ensures users are warned appropriately even when only a fraction of the cache is dirty, and provides accurate warnings during `AssumeUTXO` loads.

Co-authored-by: l0rinc <pap.lorinc@gmail.com>

src/coins.cpp

@@ -76,9 +76,6 @@ void CCoinsViewCache::AddCoin(const COutPoint &outpoint, Coin&& coin, bool possi
     bool inserted;
     std::tie(it, inserted) = cacheCoins.emplace(std::piecewise_construct, std::forward_as_tuple(outpoint), std::tuple<>());
     bool fresh = false;
-    if (!inserted) {
-        cachedCoinsUsage -= it->second.coin.DynamicMemoryUsage();
-    }
     if (!possible_overwrite) {
         if (!it->second.coin.IsSpent()) {
             throw std::logic_error("Attempted to overwrite an unspent coin (when possible_overwrite is false)");
@@ -98,8 +95,13 @@ void CCoinsViewCache::AddCoin(const COutPoint &outpoint, Coin&& coin, bool possi
         // DIRTY, then it can be marked FRESH.
         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,
@@ -111,9 +113,13 @@ void CCoinsViewCache::AddCoin(const COutPoint &outpoint, Coin&& coin, bool possi
 }
 
 void CCoinsViewCache::EmplaceCoinInternalDANGER(COutPoint&& outpoint, Coin&& coin) {
-    cachedCoinsUsage += coin.DynamicMemoryUsage();
+    const auto mem_usage{coin.DynamicMemoryUsage()};
     auto [it, inserted] = cacheCoins.try_emplace(std::move(outpoint), std::move(coin));
-    if (inserted) CCoinsCacheEntry::SetDirty(*it, m_sentinel);
+    if (inserted) {
+        CCoinsCacheEntry::SetDirty(*it, m_sentinel);
+        ++m_dirty_count;
+        cachedCoinsUsage += mem_usage;
+    }
 }
 
 void AddCoins(CCoinsViewCache& cache, const CTransaction &tx, int nHeight, bool check_for_overwrite) {
@@ -130,6 +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(),
@@ -144,6 +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;
@@ -202,8 +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
@@ -222,6 +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 {
@@ -235,7 +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
@@ -248,21 +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");
@@ -306,6 +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{};
@@ -316,6 +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;
@@ -327,6 +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;
     }
@@ -343,6 +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());

src/coins.h

@@ -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) {
@@ -298,8 +300,11 @@ struct CoinsViewCacheCursor
     }
 
     inline bool WillErase(CoinsCachePair& current) const noexcept { return m_will_erase || current.second.coin.IsSpent(); }
+    size_t GetDirtyCount() const noexcept { return m_dirty_count; }
+    size_t GetTotalCount() const noexcept { return m_map.size(); }
 private:
     size_t& m_usage;
+    size_t& m_dirty_count;
     CoinsCachePair& m_sentinel;
     CCoinsMap& m_map;
     bool m_will_erase;
@@ -377,6 +382,8 @@ 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 +470,9 @@ 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;
 

src/test/coins_tests.cpp

@@ -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
@@ -194,8 +195,11 @@ void SimulationTest(CCoinsView* base, bool fake_best_block)
                     (coin.IsSpent() ? added_an_entry : updated_an_entry) = true;
                     coin = newcoin;
                 }
-                bool is_overwrite = !coin.IsSpent() || m_rng.rand32() & 1;
-                stack.back()->AddCoin(COutPoint(txid, 0), std::move(newcoin), is_overwrite);
+                if (COutPoint op(txid, 0); !stack.back()->map().contains(op) && !coin.IsSpent() && m_rng.randbool()) {
+                    stack.back()->EmplaceCoinInternalDANGER(std::move(op), std::move(newcoin));
+                } else {
+                    stack.back()->AddCoin(std::move(op), std::move(newcoin), /*possible_overwrite=*/!coin.IsSpent() || m_rng.randbool());
+                }
             } else {
                 // Spend the coin.
                 removed_an_entry = true;
@@ -663,7 +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, {}));
 }
 
@@ -674,7 +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;

src/test/fuzz/coins_view.cpp

@@ -132,6 +132,7 @@ 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)
@@ -153,10 +154,11 @@ 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().

src/txdb.cpp

@@ -8,6 +8,7 @@
 #include <coins.h>
 #include <dbwrapper.h>
 #include <logging.h>
+#include <logging/timer.h>
 #include <primitives/transaction.h>
 #include <random.h>
 #include <serialize.h>
@@ -25,6 +26,9 @@ static constexpr uint8_t DB_HEAD_BLOCKS{'H'};
 // Keys used in previous version that might still be found in the DB:
 static constexpr uint8_t DB_COINS{'c'};
 
+// Threshold for warning when writing this many dirty cache entries to disk.
+static constexpr size_t WARN_FLUSH_COINS_COUNT{10'000'000};
+
 bool CCoinsViewDB::NeedsUpgrade()
 {
     std::unique_ptr<CDBIterator> cursor{m_db->NewIterator()};
@@ -93,7 +97,7 @@ std::vector<uint256> CCoinsViewDB::GetHeadBlocks() const {
 bool CCoinsViewDB::BatchWrite(CoinsViewCacheCursor& cursor, const uint256 &hashBlock) {
     CDBBatch batch(*m_db);
     size_t count = 0;
-    size_t changed = 0;
+    const size_t dirty_count{cursor.GetDirtyCount()};
     assert(!hashBlock.IsNull());
 
     uint256 old_tip = GetBestBlock();
@@ -109,6 +113,10 @@ bool CCoinsViewDB::BatchWrite(CoinsViewCacheCursor& cursor, const uint256 &hashB
         }
     }
 
+    if (dirty_count > WARN_FLUSH_COINS_COUNT) LogWarning("Flushing large (%d entries) UTXO set to disk, it may take several minutes", dirty_count);
+    LOG_TIME_MILLIS_WITH_CATEGORY(strprintf("write coins cache to disk (%d out of %d cached coins)",
+        dirty_count, cursor.GetTotalCount()), BCLog::BENCH);
+
     // In the first batch, mark the database as being in the middle of a
     // transition from old_tip to hashBlock.
     // A vector is used for future extensibility, as we may want to support
@@ -124,8 +132,6 @@ bool CCoinsViewDB::BatchWrite(CoinsViewCacheCursor& cursor, const uint256 &hashB
             } else {
                 batch.Write(entry, it->second.coin);
             }
-
-            changed++;
         }
         count++;
         it = cursor.NextAndMaybeErase(*it);
@@ -150,7 +156,7 @@ bool CCoinsViewDB::BatchWrite(CoinsViewCacheCursor& cursor, const uint256 &hashB
 
     LogDebug(BCLog::COINDB, "Writing final batch of %.2f MiB\n", batch.ApproximateSize() * (1.0 / 1048576.0));
     bool ret = m_db->WriteBatch(batch);
-    LogDebug(BCLog::COINDB, "Committed %u changed transaction outputs (out of %u) to coin database...\n", (unsigned int)changed, (unsigned int)count);
+    LogDebug(BCLog::COINDB, "Committed %u changed transaction outputs (out of %u) to coin database...", (unsigned int)dirty_count, (unsigned int)count);
     return ret;
 }
 

src/validation.cpp

@@ -88,8 +88,6 @@ using node::CBlockIndexHeightOnlyComparator;
 using node::CBlockIndexWorkComparator;
 using node::SnapshotMetadata;
 
-/** Size threshold for warning about slow UTXO set flush to disk. */
-static constexpr size_t WARN_FLUSH_COINS_SIZE = 1 << 30; // 1 GiB
 /** Time window to wait between writing blocks/block index and chainstate to disk.
  *  Randomize writing time inside the window to prevent a situation where the
  *  network over time settles into a few cohorts of synchronized writers.
@@ -2772,8 +2770,8 @@ bool Chainstate::FlushStateToDisk(
     std::set<int> setFilesToPrune;
     bool full_flush_completed = false;
 
-    const size_t coins_count = CoinsTip().GetCacheSize();
-    const size_t coins_mem_usage = CoinsTip().DynamicMemoryUsage();
+    [[maybe_unused]] const size_t coins_count{CoinsTip().GetCacheSize()};
+    [[maybe_unused]] const size_t coins_mem_usage{CoinsTip().DynamicMemoryUsage()};
 
     try {
     {
@@ -2867,16 +2865,12 @@ bool Chainstate::FlushStateToDisk(
             }
 
             if (!CoinsTip().GetBestBlock().IsNull()) {
-                if (coins_mem_usage >= WARN_FLUSH_COINS_SIZE) LogWarning("Flushing large (%d GiB) UTXO set to disk, it may take several minutes", coins_mem_usage >> 30);
-                LOG_TIME_MILLIS_WITH_CATEGORY(strprintf("write coins cache to disk (%d coins, %.2fKiB)",
-                    coins_count, coins_mem_usage >> 10), BCLog::BENCH);
-
                 // Typical Coin structures on disk are around 48 bytes in size.
                 // Pushing a new one to the database can cause it to be written
                 // twice (once in the log, and once in the tables). This is already
                 // an overestimation, as most will delete an existing entry or
                 // overwrite one. Still, use a conservative safety factor of 2.
-                if (!CheckDiskSpace(m_chainman.m_options.datadir, 48 * 2 * 2 * CoinsTip().GetCacheSize())) {
+                if (!CheckDiskSpace(m_chainman.m_options.datadir, 48 * 2 * 2 * CoinsTip().GetDirtyCount())) {
                     return FatalError(m_chainman.GetNotifications(), state, _("Disk space is too low!"));
                 }
                 // Flush the chainstate (which may refer to block index entries).