Bump up version to 6.5.3

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/6194

Differential Revision: D19125292

Pulled By: ltamasi

fbshipit-source-id: d41aca2755ec4bec07feedd6b561e8d18606a931

HISTORY.md

@@ -1,5 +1,7 @@
 # Rocksdb Change Log
-## Unreleased
+## 6.5.3 (1/10/2020)
+### Bug Fixes
+* Fixed two performance issues related to memtable history trimming. First, a new SuperVersion is now created only if some memtables were actually trimmed. Second, trimming is only scheduled if there is at least one flushed memtable that is kept in memory for the purposes of transaction conflict checking.
 
 ## 6.5.2 (11/15/2019)
 ### Bug Fixes

db/db_impl/db_impl_write.cc

@@ -1499,12 +1499,14 @@ Status DBImpl::TrimMemtableHistory(WriteContext* context) {
   for (auto& cfd : cfds) {
     autovector<MemTable*> to_delete;
     cfd->imm()->TrimHistory(&to_delete, cfd->mem()->ApproximateMemoryUsage());
-    for (auto m : to_delete) {
-      delete m;
+    if (!to_delete.empty()) {
+      for (auto m : to_delete) {
+        delete m;
+      }
+      context->superversion_context.NewSuperVersion();
+      assert(context->superversion_context.new_superversion.get() != nullptr);
+      cfd->InstallSuperVersion(&context->superversion_context, &mutex_);
     }
-    context->superversion_context.NewSuperVersion();
-    assert(context->superversion_context.new_superversion.get() != nullptr);
-    cfd->InstallSuperVersion(&context->superversion_context, &mutex_);
 
     if (cfd->Unref()) {
       delete cfd;

db/memtable.h

@@ -135,7 +135,7 @@ class MemTable {
 
   // As a cheap version of `ApproximateMemoryUsage()`, this function doens't
   // require external synchronization. The value may be less accurate though
-  size_t ApproximateMemoryUsageFast() {
+  size_t ApproximateMemoryUsageFast() const {
     return approximate_memory_usage_.load(std::memory_order_relaxed);
   }
 

db/memtable_list.cc

@@ -266,7 +266,7 @@ void MemTableListVersion::Remove(MemTable* m,
 }
 
 // return the total memory usage assuming the oldest flushed memtable is dropped
-size_t MemTableListVersion::ApproximateMemoryUsageExcludingLast() {
+size_t MemTableListVersion::ApproximateMemoryUsageExcludingLast() const {
   size_t total_memtable_size = 0;
   for (auto& memtable : memlist_) {
     total_memtable_size += memtable->ApproximateMemoryUsage();
@@ -480,7 +480,7 @@ Status MemTableList::TryInstallMemtableFlushResults(
                            cfd->GetName().c_str(), m->file_number_, mem_id);
           assert(m->file_number_ > 0);
           current_->Remove(m, to_delete);
-          UpdateMemoryUsageExcludingLast();
+          UpdateCachedValuesFromMemTableListVersion();
           ResetTrimHistoryNeeded();
           ++mem_id;
         }
@@ -521,14 +521,14 @@ void MemTableList::Add(MemTable* m, autovector<MemTable*>* to_delete) {
   if (num_flush_not_started_ == 1) {
     imm_flush_needed.store(true, std::memory_order_release);
   }
-  UpdateMemoryUsageExcludingLast();
+  UpdateCachedValuesFromMemTableListVersion();
   ResetTrimHistoryNeeded();
 }
 
 void MemTableList::TrimHistory(autovector<MemTable*>* to_delete, size_t usage) {
   InstallNewVersion();
   current_->TrimHistory(to_delete, usage);
-  UpdateMemoryUsageExcludingLast();
+  UpdateCachedValuesFromMemTableListVersion();
   ResetTrimHistoryNeeded();
 }
 
@@ -543,18 +543,25 @@ size_t MemTableList::ApproximateUnflushedMemTablesMemoryUsage() {
 
 size_t MemTableList::ApproximateMemoryUsage() { return current_memory_usage_; }
 
-size_t MemTableList::ApproximateMemoryUsageExcludingLast() {
-  size_t usage =
+size_t MemTableList::ApproximateMemoryUsageExcludingLast() const {
+  const size_t usage =
       current_memory_usage_excluding_last_.load(std::memory_order_relaxed);
   return usage;
 }
 
-// Update current_memory_usage_excluding_last_, need to call whenever state
-// changes for MemtableListVersion (whenever InstallNewVersion() is called)
-void MemTableList::UpdateMemoryUsageExcludingLast() {
-  size_t total_memtable_size = current_->ApproximateMemoryUsageExcludingLast();
+bool MemTableList::HasHistory() const {
+  const bool has_history = current_has_history_.load(std::memory_order_relaxed);
+  return has_history;
+}
+
+void MemTableList::UpdateCachedValuesFromMemTableListVersion() {
+  const size_t total_memtable_size =
+      current_->ApproximateMemoryUsageExcludingLast();
   current_memory_usage_excluding_last_.store(total_memtable_size,
                                              std::memory_order_relaxed);
+
+  const bool has_history = current_->HasHistory();
+  current_has_history_.store(has_history, std::memory_order_relaxed);
 }
 
 uint64_t MemTableList::ApproximateOldestKeyTime() const {
@@ -684,7 +691,7 @@ Status InstallMemtableAtomicFlushResults(
                          cfds[i]->GetName().c_str(), m->GetFileNumber(),
                          mem_id);
         imm->current_->Remove(m, to_delete);
-        imm->UpdateMemoryUsageExcludingLast();
+        imm->UpdateCachedValuesFromMemTableListVersion();
         imm->ResetTrimHistoryNeeded();
       }
     }
@@ -727,7 +734,8 @@ void MemTableList::RemoveOldMemTables(uint64_t log_number,
       imm_flush_needed.store(false, std::memory_order_release);
     }
   }
-  UpdateMemoryUsageExcludingLast();
+
+  UpdateCachedValuesFromMemTableListVersion();
   ResetTrimHistoryNeeded();
 }
 

db/memtable_list.h

@@ -157,7 +157,11 @@ class MemTableListVersion {
   // excluding the last MemTable in memlist_history_. The reason for excluding
   // the last MemTable is to see if dropping the last MemTable will keep total
   // memory usage above or equal to max_write_buffer_size_to_maintain_
-  size_t ApproximateMemoryUsageExcludingLast();
+  size_t ApproximateMemoryUsageExcludingLast() const;
+
+  // Whether this version contains flushed memtables that are only kept around
+  // for transaction conflict checking.
+  bool HasHistory() const { return !memlist_history_.empty(); }
 
   bool MemtableLimitExceeded(size_t usage);
 
@@ -206,7 +210,8 @@ class MemTableList {
         commit_in_progress_(false),
         flush_requested_(false),
         current_memory_usage_(0),
-        current_memory_usage_excluding_last_(0) {
+        current_memory_usage_excluding_last_(0),
+        current_has_history_(false) {
     current_->Ref();
   }
 
@@ -260,11 +265,16 @@ class MemTableList {
   // Returns an estimate of the number of bytes of data in use.
   size_t ApproximateMemoryUsage();
 
-  // Returns the cached current_memory_usage_excluding_last_ value
-  size_t ApproximateMemoryUsageExcludingLast();
+  // Returns the cached current_memory_usage_excluding_last_ value.
+  size_t ApproximateMemoryUsageExcludingLast() const;
 
-  // Update current_memory_usage_excluding_last_ from MemtableListVersion
-  void UpdateMemoryUsageExcludingLast();
+  // Returns the cached current_has_history_ value.
+  bool HasHistory() const;
+
+  // Updates current_memory_usage_excluding_last_ and current_has_history_
+  // from MemTableListVersion. Must be called whenever InstallNewVersion is
+  // called.
+  void UpdateCachedValuesFromMemTableListVersion();
 
   // `usage` is the current size of the mutable Memtable. When
   // max_write_buffer_size_to_maintain is used, total size of mutable and
@@ -382,7 +392,11 @@ class MemTableList {
   // The current memory usage.
   size_t current_memory_usage_;
 
+  // Cached value of current_->ApproximateMemoryUsageExcludingLast().
   std::atomic<size_t> current_memory_usage_excluding_last_;
+
+  // Cached value of current_->HasHistory().
+  std::atomic<bool> current_has_history_;
 };
 
 // Installs memtable atomic flush results.

db/write_batch.cc

@@ -1786,14 +1786,28 @@ class MemTableInserter : public WriteBatch::Handler {
     // check if memtable_list size exceeds max_write_buffer_size_to_maintain
     if (trim_history_scheduler_ != nullptr) {
       auto* cfd = cf_mems_->current();
-      assert(cfd != nullptr);
-      if (cfd->ioptions()->max_write_buffer_size_to_maintain > 0 &&
-          cfd->mem()->ApproximateMemoryUsageFast() +
-                  cfd->imm()->ApproximateMemoryUsageExcludingLast() >=
-              static_cast<size_t>(
-                  cfd->ioptions()->max_write_buffer_size_to_maintain) &&
-          cfd->imm()->MarkTrimHistoryNeeded()) {
-        trim_history_scheduler_->ScheduleWork(cfd);
+
+      assert(cfd);
+      assert(cfd->ioptions());
+
+      const size_t size_to_maintain = static_cast<size_t>(
+          cfd->ioptions()->max_write_buffer_size_to_maintain);
+
+      if (size_to_maintain > 0) {
+        MemTableList* const imm = cfd->imm();
+        assert(imm);
+
+        if (imm->HasHistory()) {
+          const MemTable* const mem = cfd->mem();
+          assert(mem);
+
+          if (mem->ApproximateMemoryUsageFast() +
+                      imm->ApproximateMemoryUsageExcludingLast() >=
+                  size_to_maintain &&
+              imm->MarkTrimHistoryNeeded()) {
+            trim_history_scheduler_->ScheduleWork(cfd);
+          }
+        }
       }
     }
   }

include/rocksdb/version.h

@@ -6,7 +6,7 @@
 
 #define ROCKSDB_MAJOR 6
 #define ROCKSDB_MINOR 5
-#define ROCKSDB_PATCH 2
+#define ROCKSDB_PATCH 3
 
 // Do not use these. We made the mistake of declaring macros starting with
 // double underscore. Now we have to live with our choice. We'll deprecate these