434d32befe
This patch is a bag of fixes/cleanups that were omitted from the reader memory tracking series due to contributor error. It contains the following changes: * Get rid of unused `increase()` and `decrease()` methods. * Make all constructors and assignment operators `noexcept`. * Make move assignment operator safe w.r.t. self assignment. * `reset()`: consume the new amount before releasing the old amount, to prevent a transient window where new readers might be admitted. Signed-off-by: Botond Dénes <bdenes@scylladb.com> Message-Id: <20200206143007.633069-1-bdenes@scylladb.com>
122 lines
3.3 KiB
C++
122 lines
3.3 KiB
C++
/*
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* Copyright (C) 2019 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 <seastar/core/shared_ptr.hh>
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#include <seastar/core/file.hh>
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#include "seastarx.hh"
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struct reader_resources {
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int count = 0;
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ssize_t memory = 0;
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reader_resources() = default;
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reader_resources(int count, ssize_t memory)
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: count(count)
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, memory(memory) {
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}
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bool operator>=(const reader_resources& other) const {
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return count >= other.count && memory >= other.memory;
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}
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reader_resources& operator-=(const reader_resources& other) {
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count -= other.count;
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memory -= other.memory;
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return *this;
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}
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reader_resources& operator+=(const reader_resources& other) {
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count += other.count;
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memory += other.memory;
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return *this;
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}
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explicit operator bool() const {
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return count >= 0 && memory >= 0;
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}
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};
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class reader_concurrency_semaphore;
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class reader_permit {
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struct impl {
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reader_concurrency_semaphore& semaphore;
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reader_resources base_cost;
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impl(reader_concurrency_semaphore& semaphore, reader_resources base_cost);
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~impl();
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};
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friend reader_permit no_reader_permit();
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public:
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class memory_units {
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reader_concurrency_semaphore* _semaphore = nullptr;
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size_t _memory = 0;
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friend class reader_permit;
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private:
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memory_units(reader_concurrency_semaphore* semaphore, ssize_t memory) noexcept;
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public:
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memory_units(const memory_units&) = delete;
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memory_units(memory_units&&) noexcept;
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~memory_units();
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memory_units& operator=(const memory_units&) = delete;
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memory_units& operator=(memory_units&&) noexcept;
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void reset(size_t memory = 0);
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operator size_t() const {
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return _memory;
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}
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};
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private:
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lw_shared_ptr<impl> _impl;
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private:
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reader_permit() = default;
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public:
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reader_permit(reader_concurrency_semaphore& semaphore, reader_resources base_cost);
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bool operator==(const reader_permit& o) const {
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return _impl == o._impl;
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}
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operator bool() const {
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return bool(_impl);
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}
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memory_units get_memory_units(size_t memory = 0);
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void release();
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};
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reader_permit no_reader_permit();
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template <typename Char>
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temporary_buffer<Char> make_tracked_temporary_buffer(temporary_buffer<Char> buf, reader_permit& permit) {
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return temporary_buffer<Char>(buf.get_write(), buf.size(),
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make_deleter(buf.release(), [units = permit.get_memory_units(buf.size())] () mutable { units.reset(); }));
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}
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file make_tracked_file(file f, reader_permit p);
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