sync with upstream @ 21409451

Check the NEWS file for details of what changed.

git-svn-id: https://leveldb.googlecode.com/svn/trunk@28 62dab493-f737-651d-591e-8d6aee1b9529

db/db_impl.cc

@@ -126,6 +126,7 @@ DBImpl::DBImpl(const Options& options, const std::string& dbname)
       log_(NULL),
       bg_compaction_scheduled_(false),
       compacting_(false) {
+  mem_->Ref();
   has_imm_.Release_Store(NULL);
 
   // Reserve ten files or so for other uses and give the rest to TableCache.
@@ -152,8 +153,8 @@ DBImpl::~DBImpl() {
   }
 
   delete versions_;
-  delete mem_;
-  delete imm_;
+  if (mem_ != NULL) mem_->Unref();
+  if (imm_ != NULL) imm_->Unref();
   delete log_;
   delete logfile_;
   delete table_cache_;
@@ -344,7 +345,8 @@ Status DBImpl::RecoverLogFile(uint64_t log_number,
   // paranoid_checks==false so that corruptions cause entire commits
   // to be skipped instead of propagating bad information (like overly
   // large sequence numbers).
-  log::Reader reader(file, &reporter, true/*checksum*/);
+  log::Reader reader(file, &reporter, true/*checksum*/,
+                     0/*initial_offset*/);
   Log(env_, options_.info_log, "Recovering log #%llu",
       (unsigned long long) log_number);
 
@@ -364,6 +366,7 @@ Status DBImpl::RecoverLogFile(uint64_t log_number,
 
     if (mem == NULL) {
       mem = new MemTable(internal_comparator_);
+      mem->Ref();
     }
     status = WriteBatchInternal::InsertInto(&batch, mem);
     MaybeIgnoreError(&status);
@@ -384,7 +387,7 @@ Status DBImpl::RecoverLogFile(uint64_t log_number,
         // file-systems cause the DB::Open() to fail.
         break;
       }
-      delete mem;
+      mem->Unref();
       mem = NULL;
     }
   }
@@ -395,7 +398,7 @@ Status DBImpl::RecoverLogFile(uint64_t log_number,
     // file-systems cause the DB::Open() to fail.
   }
 
-  delete mem;
+  if (mem != NULL) mem->Unref();
   delete file;
   return status;
 }
@@ -443,11 +446,12 @@ Status DBImpl::CompactMemTable() {
   // Replace immutable memtable with the generated Table
   if (s.ok()) {
     edit.SetPrevLogNumber(0);
-    s = versions_->LogAndApply(&edit, imm_);
+    s = versions_->LogAndApply(&edit);
   }
 
   if (s.ok()) {
     // Commit to the new state
+    imm_->Unref();
     imm_ = NULL;
     has_imm_.Release_Store(NULL);
     DeleteObsoleteFiles();
@@ -556,7 +560,7 @@ void DBImpl::BackgroundCompaction() {
     c->edit()->DeleteFile(c->level(), f->number);
     c->edit()->AddFile(c->level() + 1, f->number, f->file_size,
                        f->smallest, f->largest);
-    status = versions_->LogAndApply(c->edit(), NULL);
+    status = versions_->LogAndApply(c->edit());
     Log(env_, options_.info_log, "Moved #%lld to level-%d %lld bytes %s\n",
         static_cast<unsigned long long>(f->number),
         c->level() + 1,
@@ -697,7 +701,7 @@ Status DBImpl::InstallCompactionResults(CompactionState* compact) {
   }
   compact->outputs.clear();
 
-  Status s = versions_->LogAndApply(compact->compaction->edit(), NULL);
+  Status s = versions_->LogAndApply(compact->compaction->edit());
   if (s.ok()) {
     compact->compaction->ReleaseInputs();
     DeleteObsoleteFiles();
@@ -754,9 +758,7 @@ Status DBImpl::DoCompactionWork(CompactionState* compact) {
     }
 
     Slice key = input->key();
-    InternalKey tmp_internal_key;
-    tmp_internal_key.DecodeFrom(key);
-    if (compact->compaction->ShouldStopBefore(tmp_internal_key) &&
+    if (compact->compaction->ShouldStopBefore(key) &&
         compact->builder != NULL) {
       status = FinishCompactionOutputFile(compact, input);
       if (!status.ok()) {
@@ -867,6 +869,9 @@ Status DBImpl::DoCompactionWork(CompactionState* compact) {
   }
   compacting_ = false;
   compacting_cv_.SignalAll();
+  VersionSet::LevelSummaryStorage tmp;
+  Log(env_, options_.info_log,
+      "compacted to: %s", versions_->LevelSummary(&tmp));
   return status;
 }
 
@@ -925,10 +930,11 @@ Status DBImpl::Get(const ReadOptions& options,
 Iterator* DBImpl::NewIterator(const ReadOptions& options) {
   SequenceNumber latest_snapshot;
   Iterator* internal_iter = NewInternalIterator(options, &latest_snapshot);
-  SequenceNumber sequence =
-      (options.snapshot ? options.snapshot->number_ : latest_snapshot);
-  return NewDBIterator(&dbname_, env_,
-                       user_comparator(), internal_iter, sequence);
+  return NewDBIterator(
+      &dbname_, env_, user_comparator(), internal_iter,
+      (options.snapshot != NULL
+       ? reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_
+       : latest_snapshot));
 }
 
 void DBImpl::Unref(void* arg1, void* arg2) {
@@ -945,7 +951,7 @@ const Snapshot* DBImpl::GetSnapshot() {
 
 void DBImpl::ReleaseSnapshot(const Snapshot* s) {
   MutexLock l(&mutex_);
-  snapshots_.Delete(s);
+  snapshots_.Delete(reinterpret_cast<const SnapshotImpl*>(s));
 }
 
 // Convenience methods
@@ -985,12 +991,26 @@ Status DBImpl::Write(const WriteOptions& options, WriteBatch* updates) {
 
 Status DBImpl::MakeRoomForWrite(bool force) {
   mutex_.AssertHeld();
+  bool allow_delay = !force;
   Status s;
   while (true) {
     if (!bg_error_.ok()) {
       // Yield previous error
       s = bg_error_;
       break;
+    } else if (
+        allow_delay &&
+        versions_->NumLevelFiles(0) >= config::kL0_SlowdownWritesTrigger) {
+      // We are getting close to hitting a hard limit on the number of
+      // L0 files.  Rather than delaying a single write by several
+      // seconds when we hit the hard limit, start delaying each
+      // individual write by 1ms to reduce latency variance.  Also,
+      // this delay hands over some CPU to the compaction thread in
+      // case it is sharing the same core as the writer.
+      mutex_.Unlock();
+      env_->SleepForMicroseconds(1000);
+      allow_delay = false;  // Do not delay a single write more than once
+      mutex_.Lock();
     } else if (!force &&
                (mem_->ApproximateMemoryUsage() <= options_.write_buffer_size)) {
       // There is room in current memtable
@@ -999,6 +1019,9 @@ Status DBImpl::MakeRoomForWrite(bool force) {
       // We have filled up the current memtable, but the previous
       // one is still being compacted, so we wait.
       compacting_cv_.Wait();
+    } else if (versions_->NumLevelFiles(0) >= config::kL0_StopWritesTrigger) {
+      // There are too many level-0 files.
+      compacting_cv_.Wait();
     } else {
       // Attempt to switch to a new memtable and trigger compaction of old
       assert(versions_->PrevLogNumber() == 0);
@@ -1011,7 +1034,7 @@ Status DBImpl::MakeRoomForWrite(bool force) {
       VersionEdit edit;
       edit.SetPrevLogNumber(versions_->LogNumber());
       edit.SetLogNumber(new_log_number);
-      s = versions_->LogAndApply(&edit, NULL);
+      s = versions_->LogAndApply(&edit);
       if (!s.ok()) {
         delete lfile;
         env_->DeleteFile(LogFileName(dbname_, new_log_number));
@@ -1024,6 +1047,7 @@ Status DBImpl::MakeRoomForWrite(bool force) {
       imm_ = mem_;
       has_imm_.Release_Store(imm_);
       mem_ = new MemTable(internal_comparator_);
+      mem_->Ref();
       force = false;   // Do not force another compaction if have room
       MaybeScheduleCompaction();
     }
@@ -1141,10 +1165,11 @@ Status DB::Open(const Options& options, const std::string& dbname,
       edit.SetLogNumber(new_log_number);
       impl->logfile_ = lfile;
       impl->log_ = new log::Writer(lfile);
-      s = impl->versions_->LogAndApply(&edit, NULL);
+      s = impl->versions_->LogAndApply(&edit);
     }
     if (s.ok()) {
       impl->DeleteObsoleteFiles();
+      impl->MaybeScheduleCompaction();
     }
   }
   impl->mutex_.Unlock();
@@ -1156,6 +1181,9 @@ Status DB::Open(const Options& options, const std::string& dbname,
   return s;
 }
 
+Snapshot::~Snapshot() {
+}
+
 Status DestroyDB(const std::string& dbname, const Options& options) {
   Env* env = options.env;
   std::vector<std::string> filenames;