rocksdb/db/write_controller.cc
Igor Canadi a2bb7c3c33 Push- instead of pull-model for managing Write stalls
Summary:
Introducing WriteController, which is a source of truth about per-DB write delays. Let's define an DB epoch as a period where there are no flushes and compactions (i.e. new epoch is started when flush or compaction finishes). Each epoch can either:
* proceed with all writes without delay
* delay all writes by fixed time
* stop all writes

The three modes are recomputed at each epoch change (flush, compaction), rather than on every write (which is currently the case).

When we have a lot of column families, our current pull behavior adds a big overhead, since we need to loop over every column family for every write. With new push model, overhead on Write code-path is minimal.

This is just the start. Next step is to also take care of stalls introduced by slow memtable flushes. The final goal is to eliminate function MakeRoomForWrite(), which currently needs to be called for every column family by every write.

Test Plan: make check for now. I'll add some unit tests later. Also, perf test.

Reviewers: dhruba, yhchiang, MarkCallaghan, sdong, ljin

Reviewed By: ljin

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D22791
2014-09-08 11:20:25 -07:00

38 lines
1.2 KiB
C++

// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
#include "db/write_controller.h"
#include <cassert>
namespace rocksdb {
std::unique_ptr<WriteControllerToken> WriteController::GetStopToken() {
++total_stopped_;
return std::unique_ptr<WriteControllerToken>(new StopWriteToken(this));
}
std::unique_ptr<WriteControllerToken> WriteController::GetDelayToken(
uint64_t delay_us) {
total_delay_us_ += delay_us;
return std::unique_ptr<WriteControllerToken>(
new DelayWriteToken(this, delay_us));
}
bool WriteController::IsStopped() const { return total_stopped_ > 0; }
uint64_t WriteController::GetDelay() const { return total_delay_us_; }
StopWriteToken::~StopWriteToken() {
assert(controller_->total_stopped_ >= 1);
--controller_->total_stopped_;
}
DelayWriteToken::~DelayWriteToken() {
assert(controller_->total_delay_us_ >= delay_us_);
controller_->total_delay_us_ -= delay_us_;
}
} // namespace rocksdb