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2f41ecfe75
Summary: MyRocks currently sets `max_write_buffer_number_to_maintain` in order to maintain enough history for transaction conflict checking. The effectiveness of this approach depends on the size of memtables. When memtables are small, it may not keep enough history; when memtables are large, this may consume too much memory. We are proposing a new way to configure memtable list history: by limiting the memory usage of immutable memtables. The new option is `max_write_buffer_size_to_maintain` and it will take precedence over the old `max_write_buffer_number_to_maintain` if they are both set to non-zero values. The new option accounts for the total memory usage of flushed immutable memtables and mutable memtable. When the total usage exceeds the limit, RocksDB may start dropping immutable memtables (which is also called trimming history), starting from the oldest one. The semantics of the old option actually works both as an upper bound and lower bound. History trimming will start if number of immutable memtables exceeds the limit, but it will never go below (limit-1) due to history trimming. In order the mimic the behavior with the new option, history trimming will stop if dropping the next immutable memtable causes the total memory usage go below the size limit. For example, assuming the size limit is set to 64MB, and there are 3 immutable memtables with sizes of 20, 30, 30. Although the total memory usage is 80MB > 64MB, dropping the oldest memtable will reduce the memory usage to 60MB < 64MB, so in this case no memtable will be dropped. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5022 Differential Revision: D14394062 Pulled By: miasantreble fbshipit-source-id: 60457a509c6af89d0993f988c9b5c2aa9e45f5c5
137 lines
4.5 KiB
C++
137 lines
4.5 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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//
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#pragma once
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#include <sstream>
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#include <string>
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#include <unordered_map>
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#include <vector>
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namespace rocksdb {
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class Slice;
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extern std::vector<std::string> StringSplit(const std::string& arg, char delim);
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template <typename T>
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inline std::string ToString(T value) {
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#if !(defined OS_ANDROID) && !(defined CYGWIN) && !(defined OS_FREEBSD)
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return std::to_string(value);
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#else
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// Andorid or cygwin doesn't support all of C++11, std::to_string() being
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// one of the not supported features.
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std::ostringstream os;
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os << value;
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return os.str();
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#endif
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}
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// Append a human-readable printout of "num" to *str
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extern void AppendNumberTo(std::string* str, uint64_t num);
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// Append a human-readable printout of "value" to *str.
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// Escapes any non-printable characters found in "value".
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extern void AppendEscapedStringTo(std::string* str, const Slice& value);
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// Return a string printout of "num"
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extern std::string NumberToString(uint64_t num);
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// Return a human-readable version of num.
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// for num >= 10.000, prints "xxK"
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// for num >= 10.000.000, prints "xxM"
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// for num >= 10.000.000.000, prints "xxG"
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extern std::string NumberToHumanString(int64_t num);
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// Return a human-readable version of bytes
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// ex: 1048576 -> 1.00 GB
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extern std::string BytesToHumanString(uint64_t bytes);
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// Return a human-readable version of unix time
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// ex: 1562116015 -> "Tue Jul 2 18:06:55 2019"
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extern std::string TimeToHumanString(int unixtime);
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// Append a human-readable time in micros.
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int AppendHumanMicros(uint64_t micros, char* output, int len,
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bool fixed_format);
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// Append a human-readable size in bytes
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int AppendHumanBytes(uint64_t bytes, char* output, int len);
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// Return a human-readable version of "value".
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// Escapes any non-printable characters found in "value".
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extern std::string EscapeString(const Slice& value);
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// Parse a human-readable number from "*in" into *value. On success,
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// advances "*in" past the consumed number and sets "*val" to the
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// numeric value. Otherwise, returns false and leaves *in in an
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// unspecified state.
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extern bool ConsumeDecimalNumber(Slice* in, uint64_t* val);
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// Returns true if the input char "c" is considered as a special character
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// that will be escaped when EscapeOptionString() is called.
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//
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// @param c the input char
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// @return true if the input char "c" is considered as a special character.
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// @see EscapeOptionString
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bool isSpecialChar(const char c);
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// If the input char is an escaped char, it will return the its
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// associated raw-char. Otherwise, the function will simply return
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// the original input char.
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char UnescapeChar(const char c);
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// If the input char is a control char, it will return the its
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// associated escaped char. Otherwise, the function will simply return
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// the original input char.
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char EscapeChar(const char c);
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// Converts a raw string to an escaped string. Escaped-characters are
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// defined via the isSpecialChar() function. When a char in the input
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// string "raw_string" is classified as a special characters, then it
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// will be prefixed by '\' in the output.
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//
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// It's inverse function is UnescapeOptionString().
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// @param raw_string the input string
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// @return the '\' escaped string of the input "raw_string"
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// @see isSpecialChar, UnescapeOptionString
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std::string EscapeOptionString(const std::string& raw_string);
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// The inverse function of EscapeOptionString. It converts
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// an '\' escaped string back to a raw string.
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//
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// @param escaped_string the input '\' escaped string
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// @return the raw string of the input "escaped_string"
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std::string UnescapeOptionString(const std::string& escaped_string);
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std::string trim(const std::string& str);
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#ifndef ROCKSDB_LITE
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bool ParseBoolean(const std::string& type, const std::string& value);
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uint32_t ParseUint32(const std::string& value);
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int32_t ParseInt32(const std::string& value);
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#endif
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uint64_t ParseUint64(const std::string& value);
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int ParseInt(const std::string& value);
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int64_t ParseInt64(const std::string& value);
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double ParseDouble(const std::string& value);
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size_t ParseSizeT(const std::string& value);
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std::vector<int> ParseVectorInt(const std::string& value);
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bool SerializeIntVector(const std::vector<int>& vec, std::string* value);
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extern const std::string kNullptrString;
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} // namespace rocksdb
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