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7842920be5
Summary: We slow down data into the database to the rate of options.delayed_write_rate (a new option) with this patch. The thread synchronization approach I take is to still synchronize write controller by DB mutex and GetDelay() is inside DB mutex. Try to minimize the frequency of getting time in GetDelay(). I verified it through db_bench and it seems to work hard_rate_limit is deprecated. options.delayed_write_rate is still not dynamically changeable. Need to work on it as a follow-up. Test Plan: Add new unit tests in db_test Reviewers: yhchiang, rven, kradhakrishnan, anthony, MarkCallaghan, igor Reviewed By: igor Subscribers: ikabiljo, leveldb, dhruba Differential Revision: https://reviews.facebook.net/D36351
98 lines
3 KiB
C++
98 lines
3 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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#pragma once
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#include <stdint.h>
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#include <memory>
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namespace rocksdb {
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class Env;
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class WriteControllerToken;
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// WriteController is controlling write stalls in our write code-path. Write
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// stalls happen when compaction can't keep up with write rate.
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// All of the methods here (including WriteControllerToken's destructors) need
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// to be called while holding DB mutex
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class WriteController {
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public:
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explicit WriteController(uint64_t delayed_write_rate = 1024u * 1024u * 32u)
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: total_stopped_(0),
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total_delayed_(0),
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bytes_left_(0),
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last_refill_time_(0) {
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set_delayed_write_rate(delayed_write_rate);
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}
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~WriteController() = default;
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// When an actor (column family) requests a stop token, all writes will be
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// stopped until the stop token is released (deleted)
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std::unique_ptr<WriteControllerToken> GetStopToken();
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// When an actor (column family) requests a delay token, total delay for all
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// writes to the DB will be controlled under the delayed write rate. Every
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// write needs to call GetDelay() with number of bytes writing to the DB,
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// which returns number of microseconds to sleep.
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std::unique_ptr<WriteControllerToken> GetDelayToken();
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// these two metods are querying the state of the WriteController
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bool IsStopped() const;
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bool NeedsDelay() const { return total_delayed_ > 0; }
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// return how many microseconds the caller needs to sleep after the call
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// num_bytes: how many number of bytes to put into the DB.
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// Prerequisite: DB mutex held.
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uint64_t GetDelay(Env* env, uint64_t num_bytes);
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void set_delayed_write_rate(uint64_t delayed_write_rate) {
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delayed_write_rate_ = delayed_write_rate;
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if (delayed_write_rate_ == 0) {
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// avoid divide 0
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delayed_write_rate_ = 1U;
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}
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}
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private:
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friend class WriteControllerToken;
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friend class StopWriteToken;
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friend class DelayWriteToken;
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int total_stopped_;
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int total_delayed_;
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uint64_t bytes_left_;
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uint64_t last_refill_time_;
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uint64_t delayed_write_rate_;
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};
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class WriteControllerToken {
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public:
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explicit WriteControllerToken(WriteController* controller)
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: controller_(controller) {}
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virtual ~WriteControllerToken() {}
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protected:
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WriteController* controller_;
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private:
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// no copying allowed
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WriteControllerToken(const WriteControllerToken&) = delete;
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void operator=(const WriteControllerToken&) = delete;
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};
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class StopWriteToken : public WriteControllerToken {
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public:
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explicit StopWriteToken(WriteController* controller)
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: WriteControllerToken(controller) {}
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virtual ~StopWriteToken();
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};
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class DelayWriteToken : public WriteControllerToken {
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public:
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explicit DelayWriteToken(WriteController* controller)
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: WriteControllerToken(controller) {}
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virtual ~DelayWriteToken();
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};
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} // namespace rocksdb
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