Re: [boost] [thread] cache of initialized threads

From: James Talbut (James.Talbut_at_[hidden])
Date: 2008-05-09 05:01:26

The Windows Threadpool (from Vista onwards) has quite a lot of features
and is very usable, unfortunately prior to Vista it was much more
limited and couldn't do tracking of job completion well.
Using the threadpool involves a lot of functions calls,  mainly for
initialising static data (you create a structure and pass it to the
function to init).
The starting point is here:
http://msdn.microsoft.com/en-us/library/ms682456.aspx (though you don't
actually have to create a threadpool yourself because there is a
default).

When a job is submitted and the pool is busy it 'may' create a new
thread, depending on a private algorithm.
You use SetThreadpoolCallbackRunsLong to influence this.
Bearing in mind that thread creation is expensive (potentially much more
so than simply completing a callback) you don't want to use a naiive
implementation that always creates new threads (unless you know your
jobs are big, which a library can't know).

Obviously, being as they are Windows functions they aren't C++ specific
- the job function has a fixed signature taking a PVOID, for example.
If you need to support Windows and pthreads I wouldn't use the windows
threadpool, coming up with a suitable abstraction won't be simple - I'd
go for something built on top of boost::threads.

See here for a sample:
http://msdn.microsoft.com/en-us/library/ms686980(VS.85).aspx

HTH.

Jim 

> -----Original Message-----
> From: boost-bounces_at_[hidden] 
> [mailto:boost-bounces_at_[hidden]] On Behalf Of vicente.botet
> Sent: 09 May 2008 09:48
> To: boost_at_[hidden]
> Subject: Re: [boost] [thread] cache of initialized threads
> 
> ----- Original Message -----
> From: "James Talbut" <James.Talbut_at_[hidden]>
> To: <boost_at_[hidden]>
> Sent: Friday, May 09, 2008 9:39 AM
> Subject: Re: [boost] [thread] cache of initialized threads
> 
> 
> >> With a thread
> >> cache either the threre is a cached_thread in the pool and we
> >> use it to
> >> launch the user function, either the chached_threader will
> >> crate a new one.
> >
> > I suspect it's not going to help you much, but this is how 
> the native
> > thread pool behaves on Windows.
> >
> 
> 
> Hi Jim,
> 
> I don't know Windows at all. This is a good new, we will need only to 
> implement it for posix threads.
> 
> Could you give me some pointers?
> 
> Thanks,
> 
> Vicente 
> 
> 
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