Refactor flush request queueing and processing (#3952)

Summary:
RocksDB currently queues individual column family for flushing. This is not sufficient to support the needs of some applications that want to enforce order/dependency between column families, given that multiple foreground and background activities can trigger flushing in RocksDB.

This PR aims to address this limitation. Each flush request is described as a `FlushRequest` that can contain multiple column families. A background flushing thread pops one flush request from the queue at a time and processes it.

This PR does not enable atomic_flush yet, but is a subset of [PR 3752](https://github.com/facebook/rocksdb/pull/3752).
Pull Request resolved: https://github.com/facebook/rocksdb/pull/3952

Differential Revision: D8529933

Pulled By: riversand963

fbshipit-source-id: 78908a21e389a3a3f7de2a79bae0cd13af5f3539

db/db_impl.cc

@@ -348,9 +348,12 @@ Status DBImpl::CloseHelper() {
   flush_scheduler_.Clear();
 
   while (!flush_queue_.empty()) {
-    auto cfd = PopFirstFromFlushQueue();
-    if (cfd->Unref()) {
-      delete cfd;
+    const FlushRequest& flush_req = PopFirstFromFlushQueue();
+    for (const auto& iter : flush_req) {
+      ColumnFamilyData* cfd = iter.first;
+      if (cfd->Unref()) {
+        delete cfd;
+      }
     }
   }
   while (!compaction_queue_.empty()) {

db/db_impl.h

@@ -884,12 +884,41 @@ class DBImpl : public DB {
   Status SyncClosedLogs(JobContext* job_context);
 
   // Flush the in-memory write buffer to storage.  Switches to a new
-  // log-file/memtable and writes a new descriptor iff successful.
+  // log-file/memtable and writes a new descriptor iff successful. Then
+  // installs a new super version for the column family.
   Status FlushMemTableToOutputFile(ColumnFamilyData* cfd,
                                    const MutableCFOptions& mutable_cf_options,
                                    bool* madeProgress, JobContext* job_context,
+                                   SuperVersionContext* superversion_context,
                                    LogBuffer* log_buffer);
 
+  // Argument required by background flush thread.
+  struct BGFlushArg {
+    BGFlushArg()
+        : cfd_(nullptr), memtable_id_(0), superversion_context_(nullptr) {}
+    BGFlushArg(ColumnFamilyData* cfd, uint64_t memtable_id,
+               SuperVersionContext* superversion_context)
+        : cfd_(cfd),
+          memtable_id_(memtable_id),
+          superversion_context_(superversion_context) {}
+
+    // Column family to flush.
+    ColumnFamilyData* cfd_;
+    // Maximum ID of memtable to flush. In this column family, memtables with
+    // IDs smaller than this value must be flushed before this flush completes.
+    uint64_t memtable_id_;
+    // Pointer to a SuperVersionContext object. After flush completes, RocksDB
+    // installs a new superversion for the column family. This operation
+    // requires a SuperVersionContext object (currently embedded in JobContext).
+    SuperVersionContext* superversion_context_;
+  };
+
+  // Flush the memtables of (multiple) column families to multiple files on
+  // persistent storage.
+  Status FlushMemTablesToOutputFiles(
+      const autovector<BGFlushArg>& bg_flush_args, bool* made_progress,
+      JobContext* job_context, LogBuffer* log_buffer);
+
   // REQUIRES: log_numbers are sorted in ascending order
   Status RecoverLogFiles(const std::vector<uint64_t>& log_numbers,
                          SequenceNumber* next_sequence, bool read_only);
@@ -911,8 +940,7 @@ class DBImpl : public DB {
 
   Status ScheduleFlushes(WriteContext* context);
 
-  Status SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context,
-                        FlushReason flush_reason = FlushReason::kOthers);
+  Status SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context);
 
   // Force current memtable contents to be flushed.
   Status FlushMemTable(ColumnFamilyData* cfd, const FlushOptions& options,
@@ -923,7 +951,13 @@ class DBImpl : public DB {
   // gets flush. Otherwise, wait until the column family don't have any
   // memtable pending flush.
   Status WaitForFlushMemTable(ColumnFamilyData* cfd,
-                              const uint64_t* flush_memtable_id = nullptr);
+                              const uint64_t* flush_memtable_id = nullptr) {
+    return WaitForFlushMemTables({cfd}, {flush_memtable_id});
+  }
+  // Wait for memtables to be flushed for multiple column families.
+  Status WaitForFlushMemTables(
+      const autovector<ColumnFamilyData*>& cfds,
+      const autovector<const uint64_t*>& flush_memtable_ids);
 
   // REQUIRES: mutex locked
   Status SwitchWAL(WriteContext* write_context);
@@ -979,7 +1013,17 @@ class DBImpl : public DB {
   ColumnFamilyData* GetColumnFamilyDataByName(const std::string& cf_name);
 
   void MaybeScheduleFlushOrCompaction();
-  void SchedulePendingFlush(ColumnFamilyData* cfd, FlushReason flush_reason);
+
+  // A flush request specifies the column families to flush as well as the
+  // largest memtable id to persist for each column family. Once all the
+  // memtables whose IDs are smaller than or equal to this per-column-family
+  // specified value, this flush request is considered to have completed its
+  // work of flushing this column family. After completing the work for all
+  // column families in this request, this flush is considered complete.
+  typedef std::vector<std::pair<ColumnFamilyData*, uint64_t>> FlushRequest;
+
+  void SchedulePendingFlush(const FlushRequest& req, FlushReason flush_reason);
+
   void SchedulePendingCompaction(ColumnFamilyData* cfd);
   void SchedulePendingPurge(std::string fname, std::string dir_to_sync,
                             FileType type, uint64_t number, int job_id);
@@ -1021,8 +1065,7 @@ class DBImpl : public DB {
   // helper functions for adding and removing from flush & compaction queues
   void AddToCompactionQueue(ColumnFamilyData* cfd);
   ColumnFamilyData* PopFirstFromCompactionQueue();
-  void AddToFlushQueue(ColumnFamilyData* cfd, FlushReason flush_reason);
-  ColumnFamilyData* PopFirstFromFlushQueue();
+  FlushRequest PopFirstFromFlushQueue();
 
   // helper function to call after some of the logs_ were synced
   void MarkLogsSynced(uint64_t up_to, bool synced_dir, const Status& status);
@@ -1255,7 +1298,7 @@ class DBImpl : public DB {
   // in MaybeScheduleFlushOrCompaction()
   // invariant(column family present in flush_queue_ <==>
   // ColumnFamilyData::pending_flush_ == true)
-  std::deque<ColumnFamilyData*> flush_queue_;
+  std::deque<FlushRequest> flush_queue_;
   // invariant(column family present in compaction_queue_ <==>
   // ColumnFamilyData::pending_compaction_ == true)
   std::deque<ColumnFamilyData*> compaction_queue_;

db/db_impl_compaction_flush.cc

@@ -104,7 +104,8 @@ Status DBImpl::SyncClosedLogs(JobContext* job_context) {
 
 Status DBImpl::FlushMemTableToOutputFile(
     ColumnFamilyData* cfd, const MutableCFOptions& mutable_cf_options,
-    bool* made_progress, JobContext* job_context, LogBuffer* log_buffer) {
+    bool* made_progress, JobContext* job_context,
+    SuperVersionContext* superversion_context, LogBuffer* log_buffer) {
   mutex_.AssertHeld();
   assert(cfd->imm()->NumNotFlushed() != 0);
   assert(cfd->imm()->IsFlushPending());
@@ -160,8 +161,8 @@ Status DBImpl::FlushMemTableToOutputFile(
   }
 
   if (s.ok()) {
-    InstallSuperVersionAndScheduleWork(
-        cfd, &job_context->superversion_contexts[0], mutable_cf_options);
+    InstallSuperVersionAndScheduleWork(cfd, superversion_context,
+                                       mutable_cf_options);
     if (made_progress) {
       *made_progress = 1;
     }
@@ -200,6 +201,25 @@ Status DBImpl::FlushMemTableToOutputFile(
   return s;
 }
 
+Status DBImpl::FlushMemTablesToOutputFiles(
+    const autovector<BGFlushArg>& bg_flush_args, bool* made_progress,
+    JobContext* job_context, LogBuffer* log_buffer) {
+  Status s;
+  for (auto& arg : bg_flush_args) {
+    ColumnFamilyData* cfd = arg.cfd_;
+    const MutableCFOptions& mutable_cf_options =
+        *cfd->GetLatestMutableCFOptions();
+    SuperVersionContext* superversion_context = arg.superversion_context_;
+    s = FlushMemTableToOutputFile(cfd, mutable_cf_options, made_progress,
+                                  job_context, superversion_context,
+                                  log_buffer);
+    if (!s.ok()) {
+      break;
+    }
+  }
+  return s;
+}
+
 void DBImpl::NotifyOnFlushBegin(ColumnFamilyData* cfd, FileMetaData* file_meta,
                                 const MutableCFOptions& mutable_cf_options,
                                 int job_id, TableProperties prop) {
@@ -1077,63 +1097,93 @@ Status DBImpl::FlushMemTable(ColumnFamilyData* cfd,
                              FlushReason flush_reason, bool writes_stopped) {
   Status s;
   uint64_t flush_memtable_id = 0;
+  FlushRequest flush_req;
   {
     WriteContext context;
     InstrumentedMutexLock guard_lock(&mutex_);
 
-    if (cfd->imm()->NumNotFlushed() == 0 && cfd->mem()->IsEmpty() &&
-        cached_recoverable_state_empty_.load()) {
-      // Nothing to flush
-      return Status::OK();
-    }
-
     WriteThread::Writer w;
     if (!writes_stopped) {
       write_thread_.EnterUnbatched(&w, &mutex_);
     }
 
-    // SwitchMemtable() will release and reacquire mutex during execution
-    s = SwitchMemtable(cfd, &context);
-    flush_memtable_id = cfd->imm()->GetLatestMemTableID();
+    if (cfd->imm()->NumNotFlushed() != 0 || !cfd->mem()->IsEmpty() ||
+        !cached_recoverable_state_empty_.load()) {
+      s = SwitchMemtable(cfd, &context);
+      flush_memtable_id = cfd->imm()->GetLatestMemTableID();
+      flush_req.emplace_back(cfd, flush_memtable_id);
+    }
+
+    if (s.ok() && !flush_req.empty()) {
+      for (auto& elem : flush_req) {
+        ColumnFamilyData* loop_cfd = elem.first;
+        loop_cfd->imm()->FlushRequested();
+      }
+      SchedulePendingFlush(flush_req, flush_reason);
+      MaybeScheduleFlushOrCompaction();
+    }
 
     if (!writes_stopped) {
       write_thread_.ExitUnbatched(&w);
     }
-
-    cfd->imm()->FlushRequested();
-
-    // schedule flush
-    SchedulePendingFlush(cfd, flush_reason);
-    MaybeScheduleFlushOrCompaction();
   }
 
   if (s.ok() && flush_options.wait) {
-    // Wait until the compaction completes
-    s = WaitForFlushMemTable(cfd, &flush_memtable_id);
+    autovector<ColumnFamilyData*> cfds;
+    autovector<const uint64_t*> flush_memtable_ids;
+    for (auto& iter : flush_req) {
+      cfds.push_back(iter.first);
+      flush_memtable_ids.push_back(&(iter.second));
+    }
+    s = WaitForFlushMemTables(cfds, flush_memtable_ids);
   }
   TEST_SYNC_POINT("FlushMemTableFinished");
   return s;
 }
 
-Status DBImpl::WaitForFlushMemTable(ColumnFamilyData* cfd,
-                                    const uint64_t* flush_memtable_id) {
-  Status s;
+// Wait for memtables to be flushed for multiple column families.
+// let N = cfds.size()
+// for i in [0, N),
+//  1) if flush_memtable_ids[i] is not null, then the memtables with lower IDs
+//     have to be flushed for THIS column family;
+//  2) if flush_memtable_ids[i] is null, then all memtables in THIS column
+//     family have to be flushed.
+// Finish waiting when ALL column families finish flushing memtables.
+Status DBImpl::WaitForFlushMemTables(
+    const autovector<ColumnFamilyData*>& cfds,
+    const autovector<const uint64_t*>& flush_memtable_ids) {
+  int num = static_cast<int>(cfds.size());
   // Wait until the compaction completes
   InstrumentedMutexLock l(&mutex_);
-  while (cfd->imm()->NumNotFlushed() > 0 && !error_handler_.IsDBStopped() &&
-         (flush_memtable_id == nullptr ||
-          cfd->imm()->GetEarliestMemTableID() <= *flush_memtable_id)) {
+  while (!error_handler_.IsDBStopped()) {
     if (shutting_down_.load(std::memory_order_acquire)) {
       return Status::ShutdownInProgress();
     }
-    if (cfd->IsDropped()) {
-      // FlushJob cannot flush a dropped CF, if we did not break here
-      // we will loop forever since cfd->imm()->NumNotFlushed() will never
-      // drop to zero
+    // Number of column families that have been dropped.
+    int num_dropped = 0;
+    // Number of column families that have finished flush.
+    int num_finished = 0;
+    for (int i = 0; i < num; ++i) {
+      if (cfds[i]->IsDropped()) {
+        ++num_dropped;
+      } else if (cfds[i]->imm()->NumNotFlushed() == 0 ||
+                 (flush_memtable_ids[i] != nullptr &&
+                  cfds[i]->imm()->GetEarliestMemTableID() >
+                      *flush_memtable_ids[i])) {
+        ++num_finished;
+      }
+    }
+    if (1 == num_dropped && 1 == num) {
       return Status::InvalidArgument("Cannot flush a dropped CF");
     }
+    // Column families involved in this flush request have either been dropped
+    // or finished flush. Then it's time to finish waiting.
+    if (num_dropped + num_finished == num) {
+      break;
+    }
     bg_cv_.Wait();
   }
+  Status s;
   if (error_handler_.IsDBStopped()) {
     s = error_handler_.GetBGError();
   }
@@ -1172,7 +1222,6 @@ void DBImpl::MaybeScheduleFlushOrCompaction() {
       env_->GetBackgroundThreads(Env::Priority::HIGH) == 0;
   while (!is_flush_pool_empty && unscheduled_flushes_ > 0 &&
          bg_flush_scheduled_ < bg_job_limits.max_flushes) {
-    unscheduled_flushes_--;
     bg_flush_scheduled_++;
     env_->Schedule(&DBImpl::BGWorkFlush, this, Env::Priority::HIGH, this);
   }
@@ -1183,7 +1232,6 @@ void DBImpl::MaybeScheduleFlushOrCompaction() {
     while (unscheduled_flushes_ > 0 &&
            bg_flush_scheduled_ + bg_compaction_scheduled_ <
                bg_job_limits.max_flushes) {
-      unscheduled_flushes_--;
       bg_flush_scheduled_++;
       env_->Schedule(&DBImpl::BGWorkFlush, this, Env::Priority::LOW, this);
     }
@@ -1260,30 +1308,28 @@ ColumnFamilyData* DBImpl::PopFirstFromCompactionQueue() {
   return cfd;
 }
 
-void DBImpl::AddToFlushQueue(ColumnFamilyData* cfd, FlushReason flush_reason) {
-  assert(!cfd->queued_for_flush());
-  cfd->Ref();
-  flush_queue_.push_back(cfd);
-  cfd->set_queued_for_flush(true);
-  cfd->SetFlushReason(flush_reason);
-}
-
-ColumnFamilyData* DBImpl::PopFirstFromFlushQueue() {
+DBImpl::FlushRequest DBImpl::PopFirstFromFlushQueue() {
   assert(!flush_queue_.empty());
-  auto cfd = *flush_queue_.begin();
+  FlushRequest flush_req = flush_queue_.front();
+  assert(unscheduled_flushes_ >= static_cast<int>(flush_req.size()));
+  unscheduled_flushes_ -= static_cast<int>(flush_req.size());
   flush_queue_.pop_front();
-  assert(cfd->queued_for_flush());
-  cfd->set_queued_for_flush(false);
   // TODO: need to unset flush reason?
-  return cfd;
+  return flush_req;
 }
 
-void DBImpl::SchedulePendingFlush(ColumnFamilyData* cfd,
+void DBImpl::SchedulePendingFlush(const FlushRequest& flush_req,
                                   FlushReason flush_reason) {
-  if (!cfd->queued_for_flush() && cfd->imm()->IsFlushPending()) {
-    AddToFlushQueue(cfd, flush_reason);
-    ++unscheduled_flushes_;
+  if (flush_req.empty()) {
+    return;
+  }
+  for (auto& iter : flush_req) {
+    ColumnFamilyData* cfd = iter.first;
+    cfd->Ref();
+    cfd->SetFlushReason(flush_reason);
   }
+  unscheduled_flushes_ += static_cast<int>(flush_req.size());
+  flush_queue_.push_back(flush_req);
 }
 
 void DBImpl::SchedulePendingCompaction(ColumnFamilyData* cfd) {
@@ -1367,40 +1413,55 @@ Status DBImpl::BackgroundFlush(bool* made_progress, JobContext* job_context,
     return status;
   }
 
-  ColumnFamilyData* cfd = nullptr;
+  autovector<BGFlushArg> bg_flush_args;
+  std::vector<SuperVersionContext>& superversion_contexts =
+      job_context->superversion_contexts;
   while (!flush_queue_.empty()) {
     // This cfd is already referenced
-    auto first_cfd = PopFirstFromFlushQueue();
-
-    if (first_cfd->IsDropped() || !first_cfd->imm()->IsFlushPending()) {
-      // can't flush this CF, try next one
-      if (first_cfd->Unref()) {
-        delete first_cfd;
+    const FlushRequest& flush_req = PopFirstFromFlushQueue();
+    superversion_contexts.clear();
+    superversion_contexts.reserve(flush_req.size());
+
+    for (const auto& iter : flush_req) {
+      ColumnFamilyData* cfd = iter.first;
+      if (cfd->IsDropped() || !cfd->imm()->IsFlushPending()) {
+        // can't flush this CF, try next one
+        if (cfd->Unref()) {
+          delete cfd;
+        }
+        continue;
       }
-      continue;
+      superversion_contexts.emplace_back(SuperVersionContext(true));
+      bg_flush_args.emplace_back(cfd, iter.second,
+                                 &(superversion_contexts.back()));
+    }
+    if (!bg_flush_args.empty()) {
+      break;
     }
-
-    // found a flush!
-    cfd = first_cfd;
-    break;
   }
 
-  if (cfd != nullptr) {
-    const MutableCFOptions mutable_cf_options =
-        *cfd->GetLatestMutableCFOptions();
+  if (!bg_flush_args.empty()) {
     auto bg_job_limits = GetBGJobLimits();
-    ROCKS_LOG_BUFFER(
-        log_buffer,
-        "Calling FlushMemTableToOutputFile with column "
-        "family [%s], flush slots available %d, compaction slots available %d, "
-        "flush slots scheduled %d, compaction slots scheduled %d",
-        cfd->GetName().c_str(), bg_job_limits.max_flushes,
-        bg_job_limits.max_compactions, bg_flush_scheduled_,
-        bg_compaction_scheduled_);
-    status = FlushMemTableToOutputFile(cfd, mutable_cf_options, made_progress,
-                                       job_context, log_buffer);
-    if (cfd->Unref()) {
-      delete cfd;
+    for (const auto& arg : bg_flush_args) {
+      ColumnFamilyData* cfd = arg.cfd_;
+      ROCKS_LOG_BUFFER(
+          log_buffer,
+          "Calling FlushMemTableToOutputFile with column "
+          "family [%s], flush slots available %d, compaction slots available "
+          "%d, "
+          "flush slots scheduled %d, compaction slots scheduled %d",
+          cfd->GetName().c_str(), bg_job_limits.max_flushes,
+          bg_job_limits.max_compactions, bg_flush_scheduled_,
+          bg_compaction_scheduled_);
+    }
+    status = FlushMemTablesToOutputFiles(bg_flush_args, made_progress,
+                                         job_context, log_buffer);
+    for (auto& arg : bg_flush_args) {
+      ColumnFamilyData* cfd = arg.cfd_;
+      if (cfd->Unref()) {
+        delete cfd;
+        arg.cfd_ = nullptr;
+      }
     }
   }
   return status;
@@ -2080,7 +2141,10 @@ bool DBImpl::MCOverlap(ManualCompactionState* m, ManualCompactionState* m1) {
 
 void DBImpl::InstallSuperVersionAndScheduleWork(
     ColumnFamilyData* cfd, SuperVersionContext* sv_context,
-    const MutableCFOptions& mutable_cf_options, FlushReason flush_reason) {
+    const MutableCFOptions& mutable_cf_options,
+    FlushReason /* flush_reason */) {
+  // TODO(yanqin) investigate if 'flush_reason' can be removed since it's not
+  // used.
   mutex_.AssertHeld();
 
   // Update max_total_in_memory_state_
@@ -2099,7 +2163,6 @@ void DBImpl::InstallSuperVersionAndScheduleWork(
 
   // Whenever we install new SuperVersion, we might need to issue new flushes or
   // compactions.
-  SchedulePendingFlush(cfd, flush_reason);
   SchedulePendingCompaction(cfd);
   MaybeScheduleFlushOrCompaction();
 

db/db_impl_write.cc

@@ -1064,6 +1064,7 @@ Status DBImpl::SwitchWAL(WriteContext* write_context) {
                  oldest_alive_log, total_log_size_.load(), GetMaxTotalWalSize());
   // no need to refcount because drop is happening in write thread, so can't
   // happen while we're in the write thread
+  FlushRequest flush_req;
   for (auto cfd : *versions_->GetColumnFamilySet()) {
     if (cfd->IsDropped()) {
       continue;
@@ -1073,11 +1074,14 @@ Status DBImpl::SwitchWAL(WriteContext* write_context) {
       if (!status.ok()) {
         break;
       }
+      flush_req.emplace_back(cfd, cfd->imm()->GetLatestMemTableID());
       cfd->imm()->FlushRequested();
-      SchedulePendingFlush(cfd, FlushReason::kWriteBufferManager);
     }
   }
-  MaybeScheduleFlushOrCompaction();
+  if (status.ok()) {
+    SchedulePendingFlush(flush_req, FlushReason::kWriteBufferManager);
+    MaybeScheduleFlushOrCompaction();
+  }
   return status;
 }
 
@@ -1116,14 +1120,26 @@ Status DBImpl::HandleWriteBufferFull(WriteContext* write_context) {
       }
     }
   }
+
+  autovector<ColumnFamilyData*> cfds;
   if (cfd_picked != nullptr) {
-    status = SwitchMemtable(cfd_picked, write_context,
-                            FlushReason::kWriteBufferFull);
-    if (status.ok()) {
-      cfd_picked->imm()->FlushRequested();
-      SchedulePendingFlush(cfd_picked, FlushReason::kWriteBufferFull);
-      MaybeScheduleFlushOrCompaction();
+    cfds.push_back(cfd_picked);
+  }
+  FlushRequest flush_req;
+  for (const auto cfd : cfds) {
+    cfd->Ref();
+    status = SwitchMemtable(cfd, write_context);
+    cfd->Unref();
+    if (!status.ok()) {
+      break;
     }
+    uint64_t flush_memtable_id = cfd->imm()->GetLatestMemTableID();
+    cfd->imm()->FlushRequested();
+    flush_req.emplace_back(cfd, flush_memtable_id);
+  }
+  if (status.ok()) {
+    SchedulePendingFlush(flush_req, FlushReason::kWriteBufferFull);
+    MaybeScheduleFlushOrCompaction();
   }
   return status;
 }
@@ -1219,16 +1235,28 @@ Status DBImpl::ThrottleLowPriWritesIfNeeded(const WriteOptions& write_options,
 
 Status DBImpl::ScheduleFlushes(WriteContext* context) {
   ColumnFamilyData* cfd;
+  FlushRequest flush_req;
+  Status status;
   while ((cfd = flush_scheduler_.TakeNextColumnFamily()) != nullptr) {
-    auto status = SwitchMemtable(cfd, context, FlushReason::kWriteBufferFull);
+    status = SwitchMemtable(cfd, context);
+    bool should_schedule = true;
     if (cfd->Unref()) {
       delete cfd;
+      should_schedule = false;
     }
     if (!status.ok()) {
-      return status;
+      break;
+    }
+    if (should_schedule) {
+      uint64_t flush_memtable_id = cfd->imm()->GetLatestMemTableID();
+      flush_req.emplace_back(cfd, flush_memtable_id);
     }
   }
-  return Status::OK();
+  if (status.ok()) {
+    SchedulePendingFlush(flush_req, FlushReason::kWriteBufferFull);
+    MaybeScheduleFlushOrCompaction();
+  }
+  return status;
 }
 
 #ifndef ROCKSDB_LITE
@@ -1249,8 +1277,7 @@ void DBImpl::NotifyOnMemTableSealed(ColumnFamilyData* /*cfd*/,
 
 // REQUIRES: mutex_ is held
 // REQUIRES: this thread is currently at the front of the writer queue
-Status DBImpl::SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context,
-                              FlushReason flush_reason) {
+Status DBImpl::SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context) {
   mutex_.AssertHeld();
   WriteThread::Writer nonmem_w;
   if (two_write_queues_) {
@@ -1422,7 +1449,7 @@ Status DBImpl::SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context,
   new_mem->Ref();
   cfd->SetMemtable(new_mem);
   InstallSuperVersionAndScheduleWork(cfd, &context->superversion_context,
-                                     mutable_cf_options, flush_reason);
+                                     mutable_cf_options);
   if (two_write_queues_) {
     nonmem_write_thread_.ExitUnbatched(&nonmem_w);
   }