Keep track of memory usage in CCoinsViewCache

Author: sipa

src/coins.cpp

@@ -4,6 +4,7 @@
 
 #include "coins.h"
 
+#include "memusage.h"
 #include "random.h"
 
 #include <assert.h>
@@ -57,13 +58,17 @@ bool CCoinsViewBacked::GetStats(CCoinsStats &stats) const { return base->GetStat
 
 CCoinsKeyHasher::CCoinsKeyHasher() : salt(GetRandHash()) {}
 
-CCoinsViewCache::CCoinsViewCache(CCoinsView *baseIn) : CCoinsViewBacked(baseIn), hasModifier(false) { }
+CCoinsViewCache::CCoinsViewCache(CCoinsView *baseIn) : CCoinsViewBacked(baseIn), hasModifier(false), cachedCoinsUsage(0) { }
 
 CCoinsViewCache::~CCoinsViewCache()
 {
     assert(!hasModifier);
 }
 
+size_t CCoinsViewCache::DynamicMemoryUsage() const {
+    return memusage::DynamicUsage(cacheCoins) + cachedCoinsUsage;
+}
+
 CCoinsMap::const_iterator CCoinsViewCache::FetchCoins(const uint256 &txid) const {
     CCoinsMap::iterator it = cacheCoins.find(txid);
     if (it != cacheCoins.end())
@@ -78,6 +83,7 @@ CCoinsMap::const_iterator CCoinsViewCache::FetchCoins(const uint256 &txid) const
         // version as fresh.
         ret->second.flags = CCoinsCacheEntry::FRESH;
     }
+    cachedCoinsUsage += memusage::DynamicUsage(ret->second.coins);
     return ret;
 }
 
@@ -93,6 +99,7 @@ bool CCoinsViewCache::GetCoins(const uint256 &txid, CCoins &coins) const {
 CCoinsModifier CCoinsViewCache::ModifyCoins(const uint256 &txid) {
     assert(!hasModifier);
     std::pair<CCoinsMap::iterator, bool> ret = cacheCoins.insert(std::make_pair(txid, CCoinsCacheEntry()));
+    size_t cachedCoinUsage = 0;
     if (ret.second) {
         if (!base->GetCoins(txid, ret.first->second.coins)) {
             // The parent view does not have this entry; mark it as fresh.
@@ -102,10 +109,12 @@ CCoinsModifier CCoinsViewCache::ModifyCoins(const uint256 &txid) {
             // The parent view only has a pruned entry for this; mark it as fresh.
             ret.first->second.flags = CCoinsCacheEntry::FRESH;
         }
+    } else {
+        cachedCoinUsage = memusage::DynamicUsage(ret.first->second.coins);
     }
     // Assume that whenever ModifyCoins is called, the entry will be modified.
     ret.first->second.flags |= CCoinsCacheEntry::DIRTY;
-    return CCoinsModifier(*this, ret.first);
+    return CCoinsModifier(*this, ret.first, cachedCoinUsage);
 }
 
 const CCoins* CCoinsViewCache::AccessCoins(const uint256 &txid) const {
@@ -150,17 +159,21 @@ bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn
                     assert(it->second.flags & CCoinsCacheEntry::FRESH);
                     CCoinsCacheEntry& entry = cacheCoins[it->first];
                     entry.coins.swap(it->second.coins);
+                    cachedCoinsUsage += memusage::DynamicUsage(entry.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.
+                    cachedCoinsUsage -= memusage::DynamicUsage(itUs->second.coins);
                     cacheCoins.erase(itUs);
                 } else {
                     // A normal modification.
+                    cachedCoinsUsage -= memusage::DynamicUsage(itUs->second.coins);
                     itUs->second.coins.swap(it->second.coins);
+                    cachedCoinsUsage += memusage::DynamicUsage(itUs->second.coins);
                     itUs->second.flags |= CCoinsCacheEntry::DIRTY;
                 }
             }
@@ -175,6 +188,7 @@ bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn
 bool CCoinsViewCache::Flush() {
     bool fOk = base->BatchWrite(cacheCoins, hashBlock);
     cacheCoins.clear();
+    cachedCoinsUsage = 0;
     return fOk;
 }
 
@@ -232,7 +246,7 @@ double CCoinsViewCache::GetPriority(const CTransaction &tx, int nHeight) const
     return tx.ComputePriority(dResult);
 }
 
-CCoinsModifier::CCoinsModifier(CCoinsViewCache& cache_, CCoinsMap::iterator it_) : cache(cache_), it(it_) {
+CCoinsModifier::CCoinsModifier(CCoinsViewCache& cache_, CCoinsMap::iterator it_, size_t usage) : cache(cache_), it(it_), cachedCoinUsage(usage) {
     assert(!cache.hasModifier);
     cache.hasModifier = true;
 }
@@ -242,7 +256,11 @@ CCoinsModifier::~CCoinsModifier()
     assert(cache.hasModifier);
     cache.hasModifier = false;
     it->second.coins.Cleanup();
+    cache.cachedCoinsUsage -= cachedCoinUsage; // Subtract the old usage
     if ((it->second.flags & CCoinsCacheEntry::FRESH) && it->second.coins.IsPruned()) {
         cache.cacheCoins.erase(it);
+    } else {
+        // If the coin still exists after the modification, add the new usage
+        cache.cachedCoinsUsage += memusage::DynamicUsage(it->second.coins);
     }
 }

src/coins.h

@@ -7,6 +7,7 @@
 #define BITCOIN_COINS_H
 
 #include "compressor.h"
+#include "memusage.h"
 #include "serialize.h"
 #include "uint256.h"
 
@@ -252,6 +253,15 @@ class CCoins
                 return false;
         return true;
     }
+
+    size_t DynamicMemoryUsage() const {
+        size_t ret = memusage::DynamicUsage(vout);
+        BOOST_FOREACH(const CTxOut &out, vout) {
+            const std::vector<unsigned char> *script = &out.scriptPubKey;
+            ret += memusage::DynamicUsage(*script);
+        }
+        return ret;
+    }
 };
 
 class CCoinsKeyHasher
@@ -356,7 +366,8 @@ class CCoinsModifier
 private:
     CCoinsViewCache& cache;
     CCoinsMap::iterator it;
-    CCoinsModifier(CCoinsViewCache& cache_, CCoinsMap::iterator it_);
+    size_t cachedCoinUsage; // Cached memory usage of the CCoins object before modification
+    CCoinsModifier(CCoinsViewCache& cache_, CCoinsMap::iterator it_, size_t usage);
 
 public:
     CCoins* operator->() { return &it->second.coins; }
@@ -372,13 +383,17 @@ class CCoinsViewCache : public CCoinsViewBacked
     /* Whether this cache has an active modifier. */
     bool hasModifier;
 
+
     /**
      * Make mutable so that we can "fill the cache" even from Get-methods
      * declared as "const".  
      */
     mutable uint256 hashBlock;
     mutable CCoinsMap cacheCoins;
 
+    /* Cached dynamic memory usage for the inner CCoins objects. */
+    mutable size_t cachedCoinsUsage;
+
 public:
     CCoinsViewCache(CCoinsView *baseIn);
     ~CCoinsViewCache();
@@ -414,6 +429,9 @@ class CCoinsViewCache : public CCoinsViewBacked
     //! Calculate the size of the cache (in number of transactions)
     unsigned int GetCacheSize() const;
 
+    //! Calculate the size of the cache (in bytes)
+    size_t DynamicMemoryUsage() const;
+
     /** 
      * Amount of bitcoins coming in to a transaction
      * Note that lightweight clients may not know anything besides the hash of previous transactions,

src/test/coins_tests.cpp

@@ -59,6 +59,24 @@ class CCoinsViewTest : public CCoinsView
 
     bool GetStats(CCoinsStats& stats) const { return false; }
 };
+
+class CCoinsViewCacheTest : public CCoinsViewCache
+{
+public:
+    CCoinsViewCacheTest(CCoinsView* base) : CCoinsViewCache(base) {}
+
+    void SelfTest() const
+    {
+        // Manually recompute the dynamic usage of the whole data, and compare it.
+        size_t ret = memusage::DynamicUsage(cacheCoins);
+        for (CCoinsMap::iterator it = cacheCoins.begin(); it != cacheCoins.end(); it++) {
+            ret += memusage::DynamicUsage(it->second.coins);
+        }
+        BOOST_CHECK_EQUAL(memusage::DynamicUsage(*this), ret);
+    }
+
+};
+
 }
 
 BOOST_FIXTURE_TEST_SUITE(coins_tests, BasicTestingSetup)
@@ -90,8 +108,8 @@ BOOST_AUTO_TEST_CASE(coins_cache_simulation_test)
 
     // The cache stack.
     CCoinsViewTest base; // A CCoinsViewTest at the bottom.
-    std::vector<CCoinsViewCache*> stack; // A stack of CCoinsViewCaches on top.
-    stack.push_back(new CCoinsViewCache(&base)); // Start with one cache.
+    std::vector<CCoinsViewCacheTest*> stack; // A stack of CCoinsViewCaches on top.
+    stack.push_back(new CCoinsViewCacheTest(&base)); // Start with one cache.
 
     // Use a limited set of random transaction ids, so we do test overwriting entries.
     std::vector<uint256> txids;
@@ -136,6 +154,9 @@ BOOST_AUTO_TEST_CASE(coins_cache_simulation_test)
                     missed_an_entry = true;
                 }
             }
+            BOOST_FOREACH(const CCoinsViewCacheTest *test, stack) {
+                test->SelfTest();
+            }
         }
 
         if (insecure_rand() % 100 == 0) {
@@ -152,7 +173,7 @@ BOOST_AUTO_TEST_CASE(coins_cache_simulation_test)
                 } else {
                     removed_all_caches = true;
                 }
-                stack.push_back(new CCoinsViewCache(tip));
+                stack.push_back(new CCoinsViewCacheTest(tip));
                 if (stack.size() == 4) {
                     reached_4_caches = true;
                 }