Fix FLASH eviction issue, the algo relies on correct key count

Former-commit-id: dc260a7f44fe197b9b0022d044d559be88bf91be

src/IStorage.h

@@ -22,7 +22,7 @@ public:
     virtual void retrieve(const char *key, size_t cchKey, callbackSingle fn) const = 0;
     virtual size_t clear() = 0;
     virtual bool enumerate(callback fn) const = 0;
-    virtual size_t count(bool fStrict) const = 0;
+    virtual size_t count() const = 0;
 
     virtual void beginWriteBatch() {} // NOP
     virtual void endWriteBatch() {} // NOP

src/db.cpp

@@ -2195,7 +2195,7 @@ dict_iter redisDbPersistentData::random()
 size_t redisDbPersistentData::size() const 
 { 
     if (m_spstorage != nullptr)
-        return m_spstorage->count(false);
+        return m_spstorage->count();
     
     return dictSize(m_pdict) 
         + (m_pdbSnapshot ? (m_pdbSnapshot->size() - dictSize(m_pdictTombstone)) : 0); 

src/evict.cpp

@@ -492,14 +492,6 @@ int freeMemoryIfNeeded(void) {
 
     mem_freed = 0;
 
-    size_t maxKeys = 0;
-    size_t totalKeysFreed = 0;
-    for (int i = 0; i < cserver.dbnum; ++i)
-        maxKeys += g_pserver->db[i]->size();
-
-    // A random search is n log n, so if we run longer than this we know we're not going to terminate
-    maxKeys = static_cast<size_t>(maxKeys * (log2(maxKeys)));
-
     if (g_pserver->maxmemory_policy == MAXMEMORY_NO_EVICTION)
         goto cant_free; /* We need to free memory, but policy forbids. */
 
@@ -640,7 +632,6 @@ int freeMemoryIfNeeded(void) {
             }
 
             keys_freed++;
-            totalKeysFreed++;
 
             /* When the memory to free starts to be big enough, we may
             * start spending so much time here that is impossible to
@@ -663,16 +654,6 @@ int freeMemoryIfNeeded(void) {
             }
         }
 
-        // When using FLASH we're not actually evicting and we leave around the key
-        //  its possible we tried to evict the whole database and failed to free enough memory
-        //  quit if this happens
-        if (totalKeysFreed >= maxKeys)
-        {
-            latencyEndMonitor(latency);
-            latencyAddSampleIfNeeded("eviction-cycle",latency);
-            goto cant_free;
-        }
-
         if (keys_freed <= 0) {
             latencyEndMonitor(latency);
             latencyAddSampleIfNeeded("eviction-cycle",latency);