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construct/include/ircd/ctx_ctx.h
Jason Volk 2251595551 ircd::ctx: Add preliminary profiling system to mitigate silent degradation.
This system alerts the developer when something blocks a context from yielding
for too long or exceeds stack usage limits. More profiling can be added for
further optimization.
2016-09-27 17:27:48 -07:00

151 lines
3.7 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_CTX_H
#include <boost/asio/io_service.hpp>
#include <boost/asio/steady_timer.hpp>
#include <boost/asio/spawn.hpp>
namespace ircd {
namespace ctx {
struct ctx
{
boost::asio::steady_timer alarm; // 64B
boost::asio::yield_context *yc;
uintptr_t stack_base;
size_t stack_max;
int64_t notes; // norm: 0 = asleep; 1 = awake; inc by others; dec by self
ctx *adjoindre;
enum flags flags;
bool finished() const { return yc == nullptr; }
bool started() const { return bool(yc); }
bool wait();
void wake();
bool note();
void operator()(boost::asio::yield_context, const std::function<void ()>) noexcept;
ctx(const size_t &stack_max = DEFAULT_STACK_SIZE,
const enum flags &flags = (enum flags)0,
boost::asio::io_service *const &ios = ircd::ios);
ctx(ctx &&) noexcept = delete;
ctx(const ctx &) = delete;
};
struct continuation
{
ctx *self;
operator const boost::asio::yield_context &() const;
operator boost::asio::yield_context &();
continuation(ctx *const &self = ircd::ctx::current);
~continuation() noexcept;
};
inline
continuation::continuation(ctx *const &self)
:self{self}
{
mark(prof::event::CUR_YIELD);
assert(self != nullptr);
assert(self->notes <= 1);
ircd::ctx::current = nullptr;
}
inline
continuation::~continuation()
noexcept
{
ircd::ctx::current = self;
mark(prof::event::CUR_CONTINUE);
self->notes = 1;
}
inline
continuation::operator boost::asio::yield_context &()
{
return *self->yc;
}
inline
continuation::operator const boost::asio::yield_context &()
const
{
return *self->yc;
}
inline bool
ctx::note()
{
if(notes++ > 0)
return false;
wake();
return true;
}
inline void
ctx::wake()
try
{
alarm.cancel();
}
catch(const boost::system::system_error &e)
{
ircd::log::error("ctx::wake(%p): %s", this, e.what());
}
inline bool
ctx::wait()
{
if(--notes > 0)
return false;
boost::system::error_code ec;
alarm.async_wait(boost::asio::yield_context(continuation(this))[ec]);
assert(ec == boost::system::errc::operation_canceled ||
ec == boost::system::errc::success);
// Interruption shouldn't be used for normal operation,
// so please eat this branch misprediction.
if(unlikely(flags & INTERRUPTED))
{
mark(prof::event::CUR_INTERRUPT);
throw interrupted("ctx(%p)::wait()", (const void *)this);
}
// notes = 1; set by continuation dtor on wakeup
return true;
}
} // namespace ctx
using ctx::continuation;
using yield = boost::asio::yield_context;
} // namespace ircd