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synced 2025-02-28 09:00:12 +08:00
sync with upstream @21706995
Fixed race condition reported by Dave Smit (dizzyd@dizzyd,com) on the leveldb mailing list. We were not signalling waiters after a trivial move from level-0. The result was that in some cases (hard to reproduce), a write would get stuck forever waiting for the number of level-0 files to drop below its hard limit. The new code is simpler: there is just one condition variable instead of two, and the condition variable is signalled after every piece of background work finishes. Also, all compaction work (including for manual compactions) is done in the background thread, and therefore we can remove the "compacting_" variable. git-svn-id: https://leveldb.googlecode.com/svn/trunk@31 62dab493-f737-651d-591e-8d6aee1b9529
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c4f5514948
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@ -119,13 +119,12 @@ DBImpl::DBImpl(const Options& options, const std::string& dbname)
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db_lock_(NULL),
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db_lock_(NULL),
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shutting_down_(NULL),
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shutting_down_(NULL),
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bg_cv_(&mutex_),
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bg_cv_(&mutex_),
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compacting_cv_(&mutex_),
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mem_(new MemTable(internal_comparator_)),
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mem_(new MemTable(internal_comparator_)),
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imm_(NULL),
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imm_(NULL),
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logfile_(NULL),
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logfile_(NULL),
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log_(NULL),
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log_(NULL),
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bg_compaction_scheduled_(false),
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bg_compaction_scheduled_(false),
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compacting_(false) {
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manual_compaction_(NULL) {
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mem_->Ref();
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mem_->Ref();
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has_imm_.Release_Store(NULL);
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has_imm_.Release_Store(NULL);
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@ -141,10 +140,8 @@ DBImpl::~DBImpl() {
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// Wait for background work to finish
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// Wait for background work to finish
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mutex_.Lock();
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mutex_.Lock();
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shutting_down_.Release_Store(this); // Any non-NULL value is ok
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shutting_down_.Release_Store(this); // Any non-NULL value is ok
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if (bg_compaction_scheduled_) {
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while (bg_compaction_scheduled_) {
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while (bg_compaction_scheduled_) {
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bg_cv_.Wait();
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bg_cv_.Wait();
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}
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}
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}
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mutex_.Unlock();
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mutex_.Unlock();
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@ -437,7 +434,6 @@ Status DBImpl::WriteLevel0Table(MemTable* mem, VersionEdit* edit) {
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Status DBImpl::CompactMemTable() {
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Status DBImpl::CompactMemTable() {
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mutex_.AssertHeld();
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mutex_.AssertHeld();
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assert(imm_ != NULL);
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assert(imm_ != NULL);
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assert(compacting_);
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// Save the contents of the memtable as a new Table
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// Save the contents of the memtable as a new Table
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VersionEdit edit;
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VersionEdit edit;
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@ -457,7 +453,6 @@ Status DBImpl::CompactMemTable() {
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DeleteObsoleteFiles();
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DeleteObsoleteFiles();
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}
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}
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compacting_cv_.SignalAll(); // Wake up waiter even if there was an error
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return s;
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return s;
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}
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}
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@ -466,22 +461,18 @@ void DBImpl::TEST_CompactRange(
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const std::string& begin,
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const std::string& begin,
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const std::string& end) {
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const std::string& end) {
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MutexLock l(&mutex_);
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MutexLock l(&mutex_);
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while (compacting_) {
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while (manual_compaction_ != NULL) {
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compacting_cv_.Wait();
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bg_cv_.Wait();
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}
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}
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Compaction* c = versions_->CompactRange(
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ManualCompaction manual;
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level,
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manual.level = level;
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InternalKey(begin, kMaxSequenceNumber, kValueTypeForSeek),
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manual.begin = begin;
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InternalKey(end, 0, static_cast<ValueType>(0)));
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manual.end = end;
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manual_compaction_ = &manual;
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if (c != NULL) {
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CompactionState* compact = new CompactionState(c);
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DoCompactionWork(compact); // Ignore error in test compaction
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CleanupCompaction(compact);
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}
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// Start any background compaction that may have been delayed by this thread
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MaybeScheduleCompaction();
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MaybeScheduleCompaction();
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while (manual_compaction_ == &manual) {
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bg_cv_.Wait();
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}
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}
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}
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Status DBImpl::TEST_CompactMemTable() {
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Status DBImpl::TEST_CompactMemTable() {
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@ -490,7 +481,7 @@ Status DBImpl::TEST_CompactMemTable() {
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if (s.ok()) {
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if (s.ok()) {
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// Wait until the compaction completes
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// Wait until the compaction completes
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while (imm_ != NULL && bg_error_.ok()) {
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while (imm_ != NULL && bg_error_.ok()) {
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compacting_cv_.Wait();
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bg_cv_.Wait();
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}
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}
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if (imm_ != NULL) {
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if (imm_ != NULL) {
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s = bg_error_;
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s = bg_error_;
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@ -503,11 +494,11 @@ void DBImpl::MaybeScheduleCompaction() {
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mutex_.AssertHeld();
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mutex_.AssertHeld();
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if (bg_compaction_scheduled_) {
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if (bg_compaction_scheduled_) {
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// Already scheduled
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// Already scheduled
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} else if (compacting_) {
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// Some other thread is running a compaction. Do not conflict with it.
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} else if (shutting_down_.Acquire_Load()) {
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} else if (shutting_down_.Acquire_Load()) {
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// DB is being deleted; no more background compactions
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// DB is being deleted; no more background compactions
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} else if (imm_ == NULL && !versions_->NeedsCompaction()) {
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} else if (imm_ == NULL &&
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manual_compaction_ == NULL &&
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!versions_->NeedsCompaction()) {
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// No work to be done
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// No work to be done
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} else {
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} else {
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bg_compaction_scheduled_ = true;
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bg_compaction_scheduled_ = true;
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@ -522,38 +513,41 @@ void DBImpl::BGWork(void* db) {
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void DBImpl::BackgroundCall() {
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void DBImpl::BackgroundCall() {
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MutexLock l(&mutex_);
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MutexLock l(&mutex_);
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assert(bg_compaction_scheduled_);
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assert(bg_compaction_scheduled_);
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if (!shutting_down_.Acquire_Load() &&
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if (!shutting_down_.Acquire_Load()) {
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!compacting_) {
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BackgroundCompaction();
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BackgroundCompaction();
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}
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}
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bg_compaction_scheduled_ = false;
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bg_compaction_scheduled_ = false;
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bg_cv_.SignalAll();
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// Previous compaction may have produced too many files in a level,
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// Previous compaction may have produced too many files in a level,
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// so reschedule another compaction if needed.
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// so reschedule another compaction if needed.
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MaybeScheduleCompaction();
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MaybeScheduleCompaction();
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bg_cv_.SignalAll();
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}
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}
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void DBImpl::BackgroundCompaction() {
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void DBImpl::BackgroundCompaction() {
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mutex_.AssertHeld();
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mutex_.AssertHeld();
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assert(!compacting_);
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if (imm_ != NULL) {
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if (imm_ != NULL) {
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compacting_ = true;
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CompactMemTable();
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CompactMemTable();
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compacting_ = false;
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compacting_cv_.SignalAll();
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return;
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return;
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}
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}
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Compaction* c = versions_->PickCompaction();
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Compaction* c;
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if (c == NULL) {
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bool is_manual = (manual_compaction_ != NULL);
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// Nothing to do
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if (is_manual) {
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return;
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const ManualCompaction* m = manual_compaction_;
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c = versions_->CompactRange(
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m->level,
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InternalKey(m->begin, kMaxSequenceNumber, kValueTypeForSeek),
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InternalKey(m->end, 0, static_cast<ValueType>(0)));
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} else {
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c = versions_->PickCompaction();
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}
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}
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Status status;
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Status status;
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if (c->IsTrivialMove()) {
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if (c == NULL) {
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// Nothing to do
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} else if (!is_manual && c->IsTrivialMove()) {
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// Move file to next level
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// Move file to next level
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assert(c->num_input_files(0) == 1);
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assert(c->num_input_files(0) == 1);
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FileMetaData* f = c->input(0, 0);
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FileMetaData* f = c->input(0, 0);
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@ -561,11 +555,13 @@ void DBImpl::BackgroundCompaction() {
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c->edit()->AddFile(c->level() + 1, f->number, f->file_size,
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c->edit()->AddFile(c->level() + 1, f->number, f->file_size,
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f->smallest, f->largest);
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f->smallest, f->largest);
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status = versions_->LogAndApply(c->edit());
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status = versions_->LogAndApply(c->edit());
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Log(env_, options_.info_log, "Moved #%lld to level-%d %lld bytes %s\n",
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VersionSet::LevelSummaryStorage tmp;
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Log(env_, options_.info_log, "Moved #%lld to level-%d %lld bytes %s: %s\n",
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static_cast<unsigned long long>(f->number),
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static_cast<unsigned long long>(f->number),
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c->level() + 1,
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c->level() + 1,
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static_cast<unsigned long long>(f->file_size),
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static_cast<unsigned long long>(f->file_size),
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status.ToString().c_str());
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status.ToString().c_str(),
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versions_->LevelSummary(&tmp));
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} else {
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} else {
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CompactionState* compact = new CompactionState(c);
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CompactionState* compact = new CompactionState(c);
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status = DoCompactionWork(compact);
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status = DoCompactionWork(compact);
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@ -584,6 +580,11 @@ void DBImpl::BackgroundCompaction() {
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bg_error_ = status;
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bg_error_ = status;
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}
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}
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}
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}
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if (is_manual) {
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// Mark it as done
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manual_compaction_ = NULL;
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}
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}
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}
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void DBImpl::CleanupCompaction(CompactionState* compact) {
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void DBImpl::CleanupCompaction(CompactionState* compact) {
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@ -734,7 +735,6 @@ Status DBImpl::DoCompactionWork(CompactionState* compact) {
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}
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}
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// Release mutex while we're actually doing the compaction work
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// Release mutex while we're actually doing the compaction work
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compacting_ = true;
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mutex_.Unlock();
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mutex_.Unlock();
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Iterator* input = versions_->MakeInputIterator(compact->compaction);
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Iterator* input = versions_->MakeInputIterator(compact->compaction);
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@ -751,7 +751,7 @@ Status DBImpl::DoCompactionWork(CompactionState* compact) {
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mutex_.Lock();
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mutex_.Lock();
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if (imm_ != NULL) {
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if (imm_ != NULL) {
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CompactMemTable();
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CompactMemTable();
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compacting_cv_.SignalAll(); // Wakeup MakeRoomForWrite() if necessary
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bg_cv_.SignalAll(); // Wakeup MakeRoomForWrite() if necessary
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}
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}
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mutex_.Unlock();
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mutex_.Unlock();
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imm_micros += (env_->NowMicros() - imm_start);
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imm_micros += (env_->NowMicros() - imm_start);
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@ -867,8 +867,6 @@ Status DBImpl::DoCompactionWork(CompactionState* compact) {
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if (status.ok()) {
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if (status.ok()) {
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status = InstallCompactionResults(compact);
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status = InstallCompactionResults(compact);
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}
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}
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compacting_ = false;
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compacting_cv_.SignalAll();
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VersionSet::LevelSummaryStorage tmp;
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VersionSet::LevelSummaryStorage tmp;
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Log(env_, options_.info_log,
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Log(env_, options_.info_log,
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"compacted to: %s", versions_->LevelSummary(&tmp));
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"compacted to: %s", versions_->LevelSummary(&tmp));
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@ -1038,10 +1036,11 @@ Status DBImpl::MakeRoomForWrite(bool force) {
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} else if (imm_ != NULL) {
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} else if (imm_ != NULL) {
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// We have filled up the current memtable, but the previous
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// We have filled up the current memtable, but the previous
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// one is still being compacted, so we wait.
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// one is still being compacted, so we wait.
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compacting_cv_.Wait();
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bg_cv_.Wait();
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} else if (versions_->NumLevelFiles(0) >= config::kL0_StopWritesTrigger) {
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} else if (versions_->NumLevelFiles(0) >= config::kL0_StopWritesTrigger) {
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// There are too many level-0 files.
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// There are too many level-0 files.
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compacting_cv_.Wait();
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Log(env_, options_.info_log, "waiting...\n");
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bg_cv_.Wait();
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} else {
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} else {
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// Attempt to switch to a new memtable and trigger compaction of old
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// Attempt to switch to a new memtable and trigger compaction of old
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assert(versions_->PrevLogNumber() == 0);
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assert(versions_->PrevLogNumber() == 0);
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12
db/db_impl.h
12
db/db_impl.h
@ -119,8 +119,7 @@ class DBImpl : public DB {
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// State below is protected by mutex_
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// State below is protected by mutex_
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port::Mutex mutex_;
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port::Mutex mutex_;
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port::AtomicPointer shutting_down_;
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port::AtomicPointer shutting_down_;
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port::CondVar bg_cv_; // Signalled when !bg_compaction_scheduled_
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port::CondVar bg_cv_; // Signalled when background work finishes
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port::CondVar compacting_cv_; // Signalled when !compacting_
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MemTable* mem_;
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MemTable* mem_;
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MemTable* imm_; // Memtable being compacted
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MemTable* imm_; // Memtable being compacted
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port::AtomicPointer has_imm_; // So bg thread can detect non-NULL imm_
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port::AtomicPointer has_imm_; // So bg thread can detect non-NULL imm_
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@ -135,8 +134,13 @@ class DBImpl : public DB {
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// Has a background compaction been scheduled or is running?
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// Has a background compaction been scheduled or is running?
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bool bg_compaction_scheduled_;
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bool bg_compaction_scheduled_;
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// Is there a compaction running?
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// Information for a manual compaction
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bool compacting_;
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struct ManualCompaction {
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int level;
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std::string begin;
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std::string end;
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};
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ManualCompaction* manual_compaction_;
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VersionSet* versions_;
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VersionSet* versions_;
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