Cache some conditions for DBImpl::MakeRoomForWrite

Summary:
Task 4580155. Some conditions in DBImpl::MakeRoomForWrite can be cached in
ColumnFamilyData, because theirs value can be changed only during compaction,
adding new memtable and/or add recalculation of compaction score.

These conditions are:

cfd->imm()->size() ==  cfd->options()->max_write_buffer_number - 1
cfd->current()->NumLevelFiles(0) >=  cfd->options()->level0_stop_writes_trigger
cfd->options()->soft_rate_limit > 0.0 &&
    (score = cfd->current()->MaxCompactionScore()) >  cfd->options()->soft_rate_limit
cfd->options()->hard_rate_limit > 1.0 &&
    (score = cfd->current()->MaxCompactionScore()) >  cfd->options()->hard_rate_limit

P.S.
As it's my first diff, Siying suggested to add everybody as a reviewers
for this diff. Sorry, if I forgot someone or add someone by mistake.

Test Plan: make all check

Reviewers: haobo, xjin, dhruba, yhchiang, zagfox, ljin, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D19311

db/column_family.cc

@@ -243,6 +243,8 @@ ColumnFamilyData::ColumnFamilyData(const std::string& dbname, uint32_t id,
     const ColumnFamilyOptions* cf_options = &options_;
     cf_options->Dump(options_.info_log.get());
   }
+
+  RecalculateWriteStallConditions();
 }
 
 // DB mutex held
@@ -295,6 +297,35 @@ ColumnFamilyData::~ColumnFamilyData() {
   }
 }
 
+void ColumnFamilyData::RecalculateWriteStallConditions() {
+  need_wait_for_num_memtables_ =
+    (imm()->size() == options()->max_write_buffer_number - 1);
+
+  if (current_ != nullptr) {
+    need_wait_for_num_level0_files_ =
+      (current_->NumLevelFiles(0) >= options()->level0_stop_writes_trigger);
+  } else {
+    need_wait_for_num_level0_files_ = false;
+  }
+
+  RecalculateWriteStallRateLimitsConditions();
+}
+
+void ColumnFamilyData::RecalculateWriteStallRateLimitsConditions() {
+  if (current_ != nullptr) {
+    exceeds_hard_rate_limit_ =
+        (options()->hard_rate_limit > 1.0 &&
+         current_->MaxCompactionScore() > options()->hard_rate_limit);
+
+    exceeds_soft_rate_limit_ =
+        (options()->soft_rate_limit > 0.0 &&
+         current_->MaxCompactionScore() > options()->soft_rate_limit);
+  } else {
+    exceeds_hard_rate_limit_ = false;
+    exceeds_soft_rate_limit_ = false;
+  }
+}
+
 const EnvOptions* ColumnFamilyData::soptions() const {
   return &(column_family_set_->storage_options_);
 }
@@ -316,7 +347,9 @@ void ColumnFamilyData::CreateNewMemtable() {
 }
 
 Compaction* ColumnFamilyData::PickCompaction(LogBuffer* log_buffer) {
-  return compaction_picker_->PickCompaction(current_, log_buffer);
+  auto result = compaction_picker_->PickCompaction(current_, log_buffer);
+  RecalculateWriteStallRateLimitsConditions();
+  return result;
 }
 
 Compaction* ColumnFamilyData::CompactRange(int input_level, int output_level,
@@ -420,6 +453,9 @@ SuperVersion* ColumnFamilyData::InstallSuperVersion(
   if (column_family_set_->db_options_->allow_thread_local) {
     ResetThreadLocalSuperVersions();
   }
+
+  RecalculateWriteStallConditions();
+
   if (old_superversion != nullptr && old_superversion->Unref()) {
     old_superversion->Cleanup();
     return old_superversion;  // will let caller delete outside of mutex

db/column_family.h

@@ -229,6 +229,22 @@ class ColumnFamilyData {
     return need_slowdown_for_num_level0_files_;
   }
 
+  bool NeedWaitForNumLevel0Files() const {
+    return need_wait_for_num_level0_files_;
+  }
+
+  bool NeedWaitForNumMemtables() const {
+    return need_wait_for_num_memtables_;
+  }
+
+  bool ExceedsSoftRateLimit() const {
+    return exceeds_soft_rate_limit_;
+  }
+
+  bool ExceedsHardRateLimit() const {
+    return exceeds_hard_rate_limit_;
+  }
+
  private:
   friend class ColumnFamilySet;
   ColumnFamilyData(const std::string& dbname, uint32_t id,
@@ -238,6 +254,14 @@ class ColumnFamilyData {
                    const EnvOptions& storage_options,
                    ColumnFamilySet* column_family_set);
 
+  // Recalculate some small conditions, which are changed only during
+  // compaction, adding new memtable and/or
+  // recalculation of compaction score. These values are used in
+  // DBImpl::MakeRoomForWrite function to decide, if it need to make
+  // a write stall
+  void RecalculateWriteStallConditions();
+  void RecalculateWriteStallRateLimitsConditions();
+
   uint32_t id_;
   const std::string name_;
   Version* dummy_versions_;  // Head of circular doubly-linked list of versions.
@@ -282,6 +306,22 @@ class ColumnFamilyData {
   // we have too many level 0 files
   bool need_slowdown_for_num_level0_files_;
 
+  // These 4 variables are updated only after compaction,
+  // adding new memtable, flushing memtables to files
+  // and/or add recalculation of compaction score.
+  // That's why theirs values are cached in ColumnFamilyData.
+  // Recalculation is made by RecalculateWriteStallConditions and
+  // RecalculateWriteStallRateLimitsConditions function. They are used
+  // in DBImpl::MakeRoomForWrite function to decide, if it need
+  // to sleep during write operation
+  bool need_wait_for_num_memtables_;
+
+  bool need_wait_for_num_level0_files_;
+
+  bool exceeds_hard_rate_limit_;
+
+  bool exceeds_soft_rate_limit_;
+
   // An object that keeps all the compaction stats
   // and picks the next compaction
   std::unique_ptr<CompactionPicker> compaction_picker_;

db/db_impl.cc

@@ -4026,8 +4026,7 @@ Status DBImpl::MakeRoomForWrite(
         DelayLoggingAndReset();
       }
       break;
-    } else if (cfd->imm()->size() ==
+    } else if (cfd->NeedWaitForNumMemtables()) {
-               cfd->options()->max_write_buffer_number - 1) {
       // We have filled up the current memtable, but the previous
       // ones are still being flushed, so we wait.
       DelayLoggingAndReset();
@@ -4048,9 +4047,7 @@ Status DBImpl::MakeRoomForWrite(
                  STALL_MEMTABLE_COMPACTION_MICROS, stall);
       cfd->internal_stats()->RecordWriteStall(
           InternalStats::MEMTABLE_COMPACTION, stall);
-    } else if (cfd->current()->NumLevelFiles(0) >=
+    } else if (cfd->NeedWaitForNumLevel0Files()) {
-               cfd->options()->level0_stop_writes_trigger) {
-      // There are too many level-0 files.
       DelayLoggingAndReset();
       Log(options_.info_log, "[%s] wait for fewer level0 files...\n",
           cfd->GetName().c_str());
@@ -4064,12 +4061,10 @@ Status DBImpl::MakeRoomForWrite(
       RecordTick(options_.statistics.get(), STALL_L0_NUM_FILES_MICROS, stall);
       cfd->internal_stats()->RecordWriteStall(InternalStats::LEVEL0_NUM_FILES,
                                               stall);
-    } else if (allow_hard_rate_limit_delay &&
+    } else if (allow_hard_rate_limit_delay && cfd->ExceedsHardRateLimit()) {
-               cfd->options()->hard_rate_limit > 1.0 &&
-               (score = cfd->current()->MaxCompactionScore()) >
-                   cfd->options()->hard_rate_limit) {
       // Delay a write when the compaction score for any level is too large.
       int max_level = cfd->current()->MaxCompactionScoreLevel();
+      score = cfd->current()->MaxCompactionScore();
       mutex_.Unlock();
       uint64_t delayed;
       {
@@ -4090,10 +4085,8 @@ Status DBImpl::MakeRoomForWrite(
         allow_hard_rate_limit_delay = false;
       }
       mutex_.Lock();
-    } else if (allow_soft_rate_limit_delay &&
+    } else if (allow_soft_rate_limit_delay && cfd->ExceedsSoftRateLimit()) {
-               cfd->options()->soft_rate_limit > 0.0 &&
+      score = cfd->current()->MaxCompactionScore();
-               (score = cfd->current()->MaxCompactionScore()) >
-                   cfd->options()->soft_rate_limit) {
       // Delay a write when the compaction score for any level is too large.
       // TODO: add statistics
       mutex_.Unlock();