Re: [boost] [threads] Win32 Events on POSIX

Subject: Re: [boost] [threads] Win32 Events on POSIX
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2015-02-17 08:08:24

On 17 Feb 2015 at 10:41, Fu ji wrote:

> But I see that I started really interesting conversation. It is really hard
> to port all funtionality of WFMO because you can put as parameters:
> 
> Change notification, Console input, Event, Memory resource notification,
> Mutex, Process, Semaphore, Thread, Waitable timer.
> 
> So we can create unified API but that kind of flexibility always provide
> performance penalty. I am not sure if something equivalent in Unix can be
> implemented on low level.

BSD and OS X implements that via kqueues. Linux is actually the odd 
man out here, epoll just isn't as useful.

I believe Boost.Thread v5 intends to implement a unified wait 
composure mechanism atop the C++ 11 STL which could also be hooked by 
a Fiber implementation. Indeed, proposed Boost.Fiber I assume does 
already implement a unified wait composure system for Fiber wait 
objects.

The real bear in all these unified wait composure systems is merging 
i/o waits into the same unified wait composure system. ASIO can be 
persuaded via async_result, AFIO will get support in v1.4, but in the 
end most C++ is still using iostreams etc. That means if you block on 
i/o, your Fibers and composed waits all block too for that thread 
until the i/o returns.

Probably that means someone would have to reimplement iostreams using 
an async engine under the bonnet. Good luck finding commercial 
funding for that.

Niall

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