mirror of
https://github.com/matrix-construct/construct
synced 2024-08-23 01:54:46 +02:00
67 lines
2.8 KiB
C
67 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 {
|
||
|
namespace ctx {
|
||
|
namespace ole {
|
||
|
|
||
|
void offload(const std::function<void ()> &);
|
||
|
|
||
|
struct init
|
||
|
{
|
||
|
init();
|
||
|
~init() noexcept;
|
||
|
};
|
||
|
|
||
|
} // namespace ole
|
||
|
|
||
|
using ole::offload;
|
||
|
|
||
|
} // namespace ctx
|
||
|
} // namespace ircd
|