fcb8d040e8
Instead of lengthy blurbs, switch to single-line, machine-readable standardized (https://spdx.dev) license identifiers. The Linux kernel switched long ago, so there is strong precedent. Three cases are handled: AGPL-only, Apache-only, and dual licensed. For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0), reasoning that our changes are extensive enough to apply our license. The changes we applied mechanically with a script, except to licenses/README.md. Closes #9937
97 lines
2.4 KiB
C++
97 lines
2.4 KiB
C++
/*
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* Copyright (C) 2020-present ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: AGPL-3.0-or-later
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*/
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#pragma once
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#include <boost/intrusive/list.hpp>
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#include <seastar/core/memory.hh>
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class evictable {
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friend class lru;
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using lru_link_type = boost::intrusive::list_member_hook<
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boost::intrusive::link_mode<boost::intrusive::auto_unlink>>;
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lru_link_type _lru_link;
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protected:
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// Prevent destruction via evictable pointer. LRU is not aware of allocation strategy.
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~evictable() = default;
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public:
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evictable() = default;
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evictable(evictable&& o) noexcept;
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evictable& operator=(evictable&&) noexcept = default;
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virtual void on_evicted() noexcept = 0;
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bool is_linked() const {
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return _lru_link.is_linked();
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}
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void unlink_from_lru() {
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_lru_link.unlink();
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}
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void swap(evictable& o) noexcept {
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_lru_link.swap_nodes(o._lru_link);
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}
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};
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class lru {
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private:
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friend class evictable;
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using lru_type = boost::intrusive::list<evictable,
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boost::intrusive::member_hook<evictable, evictable::lru_link_type, &evictable::_lru_link>,
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boost::intrusive::constant_time_size<false>>; // we need this to have bi::auto_unlink on hooks.
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lru_type _list;
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public:
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using reclaiming_result = seastar::memory::reclaiming_result;
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~lru() {
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_list.clear_and_dispose([] (evictable* e) {
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e->on_evicted();
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});
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}
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void remove(evictable& e) noexcept {
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_list.erase(_list.iterator_to(e));
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}
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void add(evictable& e) noexcept {
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_list.push_back(e);
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}
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void touch(evictable& e) noexcept {
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remove(e);
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add(e);
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}
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// Evicts a single element from the LRU
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reclaiming_result evict() noexcept {
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if (_list.empty()) {
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return reclaiming_result::reclaimed_nothing;
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}
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evictable& e = _list.front();
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_list.pop_front();
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e.on_evicted();
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return reclaiming_result::reclaimed_something;
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}
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// Evicts all elements.
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// May stall the reactor, use only in tests.
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void evict_all() {
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while (evict() == reclaiming_result::reclaimed_something) {}
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}
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};
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inline
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evictable::evictable(evictable&& o) noexcept {
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if (o._lru_link.is_linked()) {
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auto prev = o._lru_link.prev_;
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o._lru_link.unlink();
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lru::lru_type::node_algorithms::link_after(prev, _lru_link.this_ptr());
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}
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}
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