Make mempurge a background process (equivalent to in-memory compaction).

db/column_family.cc

@@ -443,26 +443,17 @@ bool SuperVersion::Unref() {
   return previous_refs == 1;
 }
 
-void SuperVersion::Cleanup(const bool noImmMemoryContribution) {
+void SuperVersion::Cleanup() {
   assert(refs.load(std::memory_order_relaxed) == 0);
   // Since this SuperVersion object is being deleted,
   // decrement reference to the immutable MemtableList
   // this SV object was pointing to.
   imm->Unref(&to_delete);
   MemTable* m = mem->Unref();
   if (m != nullptr) {
-    // Typically, if the m memtable was not made
-    // immutable, and therefore was not added to the
-    // imm list, it does not contribute to the imm
-    // memory footprint (and actually is not part of
-    // the 'imm' MemtableList at all).
-    // At the moment, noImmMemoryContribution is only
-    // used by the experimental 'MemPurge' prototype.
-    if (!noImmMemoryContribution) {
-      auto* memory_usage = current->cfd()->imm()->current_memory_usage();
-      assert(*memory_usage >= m->ApproximateMemoryUsage());
-      *memory_usage -= m->ApproximateMemoryUsage();
-    }
+    auto* memory_usage = current->cfd()->imm()->current_memory_usage();
+    assert(*memory_usage >= m->ApproximateMemoryUsage());
+    *memory_usage -= m->ApproximateMemoryUsage();
     to_delete.push_back(m);
   }
   current->Unref();
@@ -1272,7 +1263,7 @@ void ColumnFamilyData::InstallSuperVersion(
 
 void ColumnFamilyData::InstallSuperVersion(
     SuperVersionContext* sv_context, InstrumentedMutex* db_mutex,
-    const MutableCFOptions& mutable_cf_options, bool noImmMemoryContribution) {
+    const MutableCFOptions& mutable_cf_options) {
   SuperVersion* new_superversion = sv_context->new_superversion.release();
   new_superversion->db_mutex = db_mutex;
   new_superversion->mutable_cf_options = mutable_cf_options;
@@ -1302,7 +1293,7 @@ void ColumnFamilyData::InstallSuperVersion(
           new_superversion->write_stall_condition, GetName(), ioptions());
     }
     if (old_superversion->Unref()) {
-      old_superversion->Cleanup(noImmMemoryContribution);
+      old_superversion->Cleanup();
       sv_context->superversions_to_free.push_back(old_superversion);
     }
   }

db/column_family.h

@@ -222,10 +222,7 @@ struct SuperVersion {
   // Cleanup unrefs mem, imm and current. Also, it stores all memtables
   // that needs to be deleted in to_delete vector. Unrefing those
   // objects needs to be done in the mutex
-  // The 'noImmMemoryContribution' is set to true if the memtable being
-  // dereferenced in this SuperVersion was not added to the Immutable
-  // memtable list.
-  void Cleanup(bool noImmMemoryContribution = false);
+  void Cleanup();
   void Init(ColumnFamilyData* new_cfd, MemTable* new_mem,
             MemTableListVersion* new_imm, Version* new_current);
 
@@ -457,8 +454,7 @@ class ColumnFamilyData {
   // IMPORTANT: Only call this from DBImpl::InstallSuperVersion()
   void InstallSuperVersion(SuperVersionContext* sv_context,
                            InstrumentedMutex* db_mutex,
-                           const MutableCFOptions& mutable_cf_options,
-                           bool noImmMemoryContribution = false);
+                           const MutableCFOptions& mutable_cf_options);
   void InstallSuperVersion(SuperVersionContext* sv_context,
                            InstrumentedMutex* db_mutex);
 
@@ -524,6 +520,7 @@ class ColumnFamilyData {
   }
 
   ThreadLocalPtr* TEST_GetLocalSV() { return local_sv_.get(); }
+  WriteBufferManager* write_buffer_mgr() { return write_buffer_manager_; }
 
  private:
   friend class ColumnFamilySet;