b9f77ba12b
Summary: It's usually hard for users to set a value of options.delayed_write_rate. With this diff, after slowdown condition triggers, we greedily reduce write rate if estimated pending compaction bytes increase. If estimated compaction pending bytes drop, we increase the write rate. Test Plan: Add a unit test Test with db_bench setting: TEST_TMPDIR=/dev/shm/ ./db_bench --benchmarks=fillrandom -num=10000000 --soft_pending_compaction_bytes_limit=1000000000 --hard_pending_compaction_bytes_limit=3000000000 --delayed_write_rate=100000000 and make sure without the commit, write stop will happen, but with the commit, it will not happen. Reviewers: igor, anthony, rven, yhchiang, kradhakrishnan, IslamAbdelRahman Reviewed By: IslamAbdelRahman Subscribers: leveldb, dhruba Differential Revision: https://reviews.facebook.net/D52131
110 lines
3.5 KiB
C++
110 lines
3.5 KiB
C++
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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#include "db/write_controller.h"
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#include <atomic>
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#include <cassert>
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#include "rocksdb/env.h"
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namespace rocksdb {
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std::unique_ptr<WriteControllerToken> WriteController::GetStopToken() {
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++total_stopped_;
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return std::unique_ptr<WriteControllerToken>(new StopWriteToken(this));
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}
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std::unique_ptr<WriteControllerToken> WriteController::GetDelayToken(
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uint64_t write_rate) {
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total_delayed_++;
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// Reset counters.
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last_refill_time_ = 0;
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bytes_left_ = 0;
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set_delayed_write_rate(write_rate);
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return std::unique_ptr<WriteControllerToken>(new DelayWriteToken(this));
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}
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bool WriteController::IsStopped() const { return total_stopped_ > 0; }
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// This is inside DB mutex, so we can't sleep and need to minimize
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// frequency to get time.
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// If it turns out to be a performance issue, we can redesign the thread
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// synchronization model here.
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// The function trust caller will sleep micros returned.
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uint64_t WriteController::GetDelay(Env* env, uint64_t num_bytes) {
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if (total_stopped_ > 0) {
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return 0;
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}
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if (total_delayed_ == 0) {
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return 0;
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}
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const uint64_t kMicrosPerSecond = 1000000;
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const uint64_t kRefillInterval = 1024U;
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if (bytes_left_ >= num_bytes) {
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bytes_left_ -= num_bytes;
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return 0;
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}
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// The frequency to get time inside DB mutex is less than one per refill
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// interval.
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auto time_now = env->NowMicros();
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uint64_t sleep_debt = 0;
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uint64_t time_since_last_refill = 0;
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if (last_refill_time_ != 0) {
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if (last_refill_time_ > time_now) {
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sleep_debt = last_refill_time_ - time_now;
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} else {
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time_since_last_refill = time_now - last_refill_time_;
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bytes_left_ +=
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static_cast<uint64_t>(static_cast<double>(time_since_last_refill) /
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kMicrosPerSecond * delayed_write_rate_);
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if (time_since_last_refill >= kRefillInterval &&
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bytes_left_ > num_bytes) {
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// If refill interval already passed and we have enough bytes
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// return without extra sleeping.
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last_refill_time_ = time_now;
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bytes_left_ -= num_bytes;
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return 0;
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}
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}
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}
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uint64_t single_refill_amount =
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delayed_write_rate_ * kRefillInterval / kMicrosPerSecond;
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if (bytes_left_ + single_refill_amount >= num_bytes) {
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// Wait until a refill interval
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// Never trigger expire for less than one refill interval to avoid to get
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// time.
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bytes_left_ = bytes_left_ + single_refill_amount - num_bytes;
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last_refill_time_ = time_now + kRefillInterval;
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return kRefillInterval + sleep_debt;
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}
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// Need to refill more than one interval. Need to sleep longer. Check
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// whether expiration will hit
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// Sleep just until `num_bytes` is allowed.
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uint64_t sleep_amount =
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static_cast<uint64_t>(num_bytes /
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static_cast<long double>(delayed_write_rate_) *
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kMicrosPerSecond) +
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sleep_debt;
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last_refill_time_ = time_now + sleep_amount;
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return sleep_amount;
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}
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StopWriteToken::~StopWriteToken() {
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assert(controller_->total_stopped_ >= 1);
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--controller_->total_stopped_;
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}
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DelayWriteToken::~DelayWriteToken() {
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controller_->total_delayed_--;
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assert(controller_->total_delayed_ >= 0);
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}
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} // namespace rocksdb
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