4469f76e7c
So far commitlog was using contiguous buffers for storing the data that is about to be written to disk. It was able to coalesce small writes so that multiple small mutations would use the same buffer, but if a muation was large the commitlog would attempt to allocate a single, appropriately large buffer. This excessively stresses the memory allocator and may cause memory fragmentation to become an issue. The solution is to use fixed-size buffers of 128 kB, which is the standard buffer size in Scylla and keep large values fragmented.
85 lines
2.4 KiB
C++
85 lines
2.4 KiB
C++
/*
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* Copyright 2016 ScyllaDB
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*/
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/*
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* This file is part of Scylla.
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*
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* Scylla is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Scylla is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <experimental/optional>
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#include "frozen_mutation.hh"
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#include "schema.hh"
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#include "stdx.hh"
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class commitlog_entry {
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stdx::optional<column_mapping> _mapping;
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frozen_mutation _mutation;
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public:
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commitlog_entry(stdx::optional<column_mapping> mapping, frozen_mutation&& mutation)
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: _mapping(std::move(mapping)), _mutation(std::move(mutation)) { }
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const stdx::optional<column_mapping>& mapping() const { return _mapping; }
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const frozen_mutation& mutation() const { return _mutation; }
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};
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class commitlog_entry_writer {
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schema_ptr _schema;
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const frozen_mutation& _mutation;
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bool _with_schema = true;
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size_t _size = std::numeric_limits<size_t>::max();
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private:
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template<typename Output>
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void serialize(Output&) const;
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void compute_size();
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public:
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commitlog_entry_writer(schema_ptr s, const frozen_mutation& fm)
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: _schema(std::move(s)), _mutation(fm)
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{}
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void set_with_schema(bool value) {
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_with_schema = value;
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compute_size();
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}
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bool with_schema() {
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return _with_schema;
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}
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schema_ptr schema() const {
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return _schema;
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}
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size_t size() const {
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assert(_size != std::numeric_limits<size_t>::max());
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return _size;
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}
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size_t mutation_size() const {
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return _mutation.representation().size();
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}
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void write(typename seastar::memory_output_stream<std::vector<temporary_buffer<char>>::iterator>& out) const;
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};
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class commitlog_entry_reader {
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commitlog_entry _ce;
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public:
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commitlog_entry_reader(const temporary_buffer<char>& buffer);
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const stdx::optional<column_mapping>& get_column_mapping() const { return _ce.mapping(); }
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const frozen_mutation& mutation() const { return _ce.mutation(); }
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};
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