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[RocksDB] move stats counting outside of mutex protected region for DB::Get()

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Summary:
As title. This is possible as tickers are atomic now.
db_bench on high qps in-memory muti-thread random get workload, showed ~5% throughput improvement.

Test Plan: make check; db_bench; db_stress

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12555
This commit is contained in:
Haobo Xu 2013-08-26 22:23:47 -07:00
parent dad2731729
commit 43eef52001
1 changed files with 22 additions and 11 deletions
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33
db/db_impl.cc
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@ -2209,7 +2209,7 @@ Status DBImpl::GetImpl(const ReadOptions& options,
StopWatch sw(env_, options_.statistics, DB_GET);
SequenceNumber snapshot;
MutexLock l(&mutex_);
mutex_.Lock();
if (options.snapshot != nullptr) {
snapshot = reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_;
} else {
@ -2254,6 +2254,9 @@ Status DBImpl::GetImpl(const ReadOptions& options,
mem->Unref();
imm.UnrefAll();
current->Unref();
mutex_.Unlock();
// Note, tickers are atomic now - no lock protection needed any more.
RecordTick(options_.statistics, NUMBER_KEYS_READ);
RecordTick(options_.statistics, BYTES_READ, value->size());
return s;
@ -2265,7 +2268,7 @@ std::vector<Status> DBImpl::MultiGet(const ReadOptions& options,
StopWatch sw(env_, options_.statistics, DB_MULTIGET);
SequenceNumber snapshot;
MutexLock l(&mutex_);
mutex_.Lock();
if (options.snapshot != nullptr) {
snapshot = reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_;
} else {
@ -2329,6 +2332,8 @@ std::vector<Status> DBImpl::MultiGet(const ReadOptions& options,
mem->Unref();
imm.UnrefAll();
current->Unref();
mutex_.Unlock();
RecordTick(options_.statistics, NUMBER_MULTIGET_CALLS);
RecordTick(options_.statistics, NUMBER_MULTIGET_KEYS_READ, numKeys);
RecordTick(options_.statistics, NUMBER_MULTIGET_BYTES_READ, bytesRead);
@ -2413,22 +2418,28 @@ Status DBImpl::Write(const WriteOptions& options, WriteBatch* my_batch) {
uint64_t last_sequence = versions_->LastSequence();
Writer* last_writer = &w;
if (status.ok() && my_batch != nullptr) { // nullptr batch is for compactions
// TODO: BuildBatchGroup physically concatenate/copy all write batches into
// a new one. Mem copy is done with the lock held. Ideally, we only need
// the lock to obtain the last_writer and the references to all batches.
// Creation (copy) of the merged batch could have been done outside of the
// lock protected region.
WriteBatch* updates = BuildBatchGroup(&last_writer);
const SequenceNumber current_sequence = last_sequence + 1;
WriteBatchInternal::SetSequence(updates, current_sequence);
int my_batch_count = WriteBatchInternal::Count(updates);
last_sequence += my_batch_count;
// Record statistics
RecordTick(options_.statistics, NUMBER_KEYS_WRITTEN, my_batch_count);
RecordTick(options_.statistics,
BYTES_WRITTEN,
WriteBatchInternal::ByteSize(updates));
// Add to log and apply to memtable. We can release the lock
// during this phase since &w is currently responsible for logging
// and protects against concurrent loggers and concurrent writes
// into mem_.
{
mutex_.Unlock();
const SequenceNumber current_sequence = last_sequence + 1;
WriteBatchInternal::SetSequence(updates, current_sequence);
int my_batch_count = WriteBatchInternal::Count(updates);
last_sequence += my_batch_count;
// Record statistics
RecordTick(options_.statistics, NUMBER_KEYS_WRITTEN, my_batch_count);
RecordTick(options_.statistics,
BYTES_WRITTEN,
WriteBatchInternal::ByteSize(updates));
if (options.disableWAL) {
flush_on_destroy_ = true;
}