Re: [boost] [afio] Formal review of Boost.AFIO

Subject: Re: [boost] [afio] Formal review of Boost.AFIO
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2015-08-31 10:25:02

On 31 Aug 2015 at 1:38, Thomas Heller wrote:

> On 08/30/2015 10:06 PM, Niall Douglas wrote:
> > 7. future.wait() very rarely blocks in your use scenario i.e. most if
> > not nearly all the time the future is ready. If you are blocking, the
> > cost of any thread sleep will always dwarf the cost of any future.
> 
> Is this really an assumption that holds when dealing with operations 
> that do file I/O? I have a hard time believing this is the general case.

Imagine the copying of a 10Mb file in 1Mb segments. You would create 
a minimum of 11 future-promise pairs, and only wait on the very last 
one.

My own benchmarking here suggested that (much) lighter weight futures 
would let me implement a much more efficient ASIO reactor than ASIO's 
and push all potential blocking to outside AFIO, perhaps right down 
to the final end user layer. Perhaps thousands of future-promise 
pairs might be created, continued from and destroyed between actual 
thread blocks. This is why I believe - currently without real world 
proof - this ought to be a big win.

Niall

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