mirror of
https://github.com/matrix-construct/construct
synced 2024-07-24 03:18:40 +02:00
66 lines
2.8 KiB
C++
66 lines
2.8 KiB
C++
/*
|
|
* Copyright (C) 2016 Charybdis Development Team
|
|
* Copyright (C) 2016 Jason Volk <jason@zemos.net>
|
|
*
|
|
* Permission to use, copy, modify, and/or distribute this software for any
|
|
* purpose with or without fee is hereby granted, provided that the above
|
|
* copyright notice and this permission notice is present in all copies.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
|
|
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
|
|
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
|
|
* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
|
|
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
|
|
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
|
|
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
|
|
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
|
|
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
* POSSIBILITY OF SUCH DAMAGE.
|
|
*
|
|
*/
|
|
|
|
#pragma once
|
|
#define HAVE_IRCD_CTX_OLE_H
|
|
|
|
/// Context OffLoad Engine (OLE).
|
|
///
|
|
/// This system allows moving a task off the main IRCd thread by passing a function to a
|
|
/// worker thread for execution. The context on the main IRCd thread yields until the offload
|
|
/// function has returned (or thrown). Please read the last paragraph and be thoroughly dissuaded
|
|
/// from temptation to abuse this.
|
|
///
|
|
/// The offload engine is for ye 'ole libraries or opaque function calls which may hang the
|
|
/// program with blocking I/O, extreme and time-consuming computation, or other uncooperative
|
|
/// behavior. IRCd is, at its core, still a single-threaded asynchronous environment and while
|
|
/// userspace context switching is provided to eliminate callbacks, the same rules for hanging
|
|
/// the program still apply.
|
|
///
|
|
/// Before using this system, do everything you possibly can to figure out if you can participate
|
|
/// directly in the main boost::asio (glorified epoll()) system. If you have access to a file
|
|
/// descriptor, socket, or similar device exposed by the library YOU DO NOT NEED THIS SYSTEM.
|
|
/// We do not *prefer* to use threads just to have them wait on I/O. This system is also not for
|
|
/// moderately expensive computation; it is alright to be fairly liberal with the main thread.
|
|
/// You must factor in the round trip costs of kernel thread context switching, cache/bus
|
|
/// transfers and contention, and whether any concurrency will really even be produced at all
|
|
/// to make a good case for an offload that doesn't hurt more than it helps. And when it hurts,
|
|
/// it hurts _everything_.
|
|
///
|
|
namespace ircd::ctx::ole
|
|
{
|
|
struct init;
|
|
|
|
void offload(const std::function<void ()> &);
|
|
}
|
|
|
|
namespace ircd::ctx
|
|
{
|
|
using ole::offload;
|
|
}
|
|
|
|
struct ircd::ctx::ole::init
|
|
{
|
|
init();
|
|
~init() noexcept;
|
|
};
|