io_priority_class.hh

/*
 * This file is open source software, licensed to you under the terms
 * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
 * distributed with this work for additional information regarding copyright
 * ownership.  You may not use this file except in compliance with the License.
 *
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
/*
 * Copyright 2021 ScyllaDB
 */
 
#pragma once
 
#ifndef SEASTAR_MODULE
#include <seastar/core/sstring.hh>
#include <seastar/core/future.hh>
#include <seastar/util/modules.hh>
 
#include <array>
#include <mutex>
#endif
 
namespace seastar {
 
class io_queue;
 
SEASTAR_MODULE_EXPORT_BEGIN
 
using io_priority_class_id = unsigned;
 
#if SEASTAR_API_LEVEL < 7
// We could very well just add the name to the io_priority_class. However, because that
// structure is passed along all the time - and sometimes we can't help but copy it, better keep
// it lean. The name won't really be used for anything other than monitoring.
class io_priority_class {
    io_priority_class_id _id;
 
    io_priority_class() = delete;
    explicit io_priority_class(io_priority_class_id id) noexcept
        : _id(id)
    { }
 
    bool rename_registered(sstring name);
 
public:
    io_priority_class_id id() const noexcept {
        return _id;
    }
 
    [[deprecated("Use scheduling_groups and API level >= 7")]]
    static io_priority_class register_one(sstring name, uint32_t shares);
 
    future<> update_shares(uint32_t shares) const;
 
    future<> update_bandwidth(uint64_t bandwidth) const;
 
    future<> rename(sstring new_name) noexcept;
 
    unsigned get_shares() const;
    sstring get_name() const;
 
private:
    struct class_info {
        unsigned shares = 0;
        sstring name;
        bool registered() const noexcept { return shares != 0; }
    };
 
    static constexpr unsigned _max_classes = 2048;
    static std::mutex _register_lock;
    static std::array<class_info, _max_classes> _infos;
 
    friend std::tuple<unsigned, sstring> get_class_info(io_priority_class_id pc);
};
 
const io_priority_class& default_priority_class();
 
#endif
 
SEASTAR_MODULE_EXPORT_END
 
namespace internal {
#if SEASTAR_API_LEVEL >= 7
struct maybe_priority_class_ref {
};
#else
struct maybe_priority_class_ref {
    const io_priority_class& pc;
    explicit maybe_priority_class_ref(const io_priority_class& p) noexcept : pc(p) {}
    maybe_priority_class_ref() noexcept : pc(default_priority_class()) {}
};
#endif
}
 
} // namespace seastar