validation: Use dirty entry count in flush warnings and disk space checks

diff --git a/src/coins.h b/src/coins.h
index 9efd23c5..8ff29605 100644
--- a/src/coins.h
+++ b/src/coins.h
@@ -293,6 +293,8 @@ 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_dirty_count;
     CoinsCachePair& m_sentinel;
diff --git a/src/txdb.cpp b/src/txdb.cpp
index 21f6eb93..2c39cf27 100644
--- a/src/txdb.cpp
+++ b/src/txdb.cpp
@@ -7,6 +7,7 @@
 
 #include <coins.h>
 #include <dbwrapper.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()};
@@ -97,7 +101,7 @@ void CCoinsViewDB::BatchWrite(CoinsViewCacheCursor& cursor, const uint256& hashB
 {
     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();
@@ -113,6 +117,10 @@ void 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
@@ -128,8 +136,6 @@ void CCoinsViewDB::BatchWrite(CoinsViewCacheCursor& cursor, const uint256& hashB
             } else {
                 batch.Write(entry, it->second.coin);
             }
-
-            changed++;
         }
         count++;
         it = cursor.NextAndMaybeErase(*it);
@@ -154,7 +160,7 @@ void CCoinsViewDB::BatchWrite(CoinsViewCacheCursor& cursor, const uint256& hashB
 
     LogDebug(BCLog::COINDB, "Writing final batch of %.2f MiB\n", batch.ApproximateSize() * (1.0 / 1048576.0));
     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);
 }
 
 size_t CCoinsViewDB::EstimateSize() const
diff --git a/src/validation.cpp b/src/validation.cpp
index c200c3d6..0a7c57df 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -89,8 +89,6 @@ 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.
@@ -2708,8 +2706,8 @@ 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 {
     {
@@ -2802,16 +2800,12 @@ 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).