From: "Jakub Pavlík jn." <severus@...>
Date: 2009-01-19T18:06:17+09:00
Subject: Re: Thread starvation

> On 18.01.2009 19:04, Jakub Pavl�k jn. wrote:
> >Hello,
> >
> >In my game freeVikings [http://freevikings.sf.net] I have code listed 
> >below.
> >It uses threads and sometimes problem known as "thread starvation" occurs.
> >Does anyone know some solution?
> >(A more detailed description is under the code listing.)
> >
> >----------------------------------
> >def do_loading(&block)
> >  Thread.abort_on_exception = true
> >
> >  load_t = Thread.new {
> >    Thread.current.priority = 1
> >    Thread.stop
> >
> >    block.call
> >  }
> >
> >  progressbar_t = Thread.new {
> >    Thread.current.priority = 2
> >    load_t.run
> >
> >    loop {
> >      paint_loading_screen @app_window, true
> >      sleep 0.3
> >    }
> >  }
> >
> >  load_t.join
> >  Thread.kill progressbar_t
> >end
> >----------------------------------
> >
> >It's an instance method of class Game and is used in this way:
> >a_game.do_loading {
> >  # load something here
> >}
> >
> >Purpose of this method is to show a simple progressbar while doing some 
> >long-lasting operation (e.g. loading new level).
> >
> >It creates two threads: load_t, in which given block is executed
> >and progressbar_t, which regularly calls Game#paint_loading_screen 
> >(method, which repaints loading screen with progressbar).
> >
> >Thread progressbar_t has higher priority, because I need it to be called
> >often and not to e.g. wait for load_t's end.
> >
> >Unfortunatelly from time to time Thread load_t is somehow "suspended" - 
> >progressbar shows progress on and on, but nothing happens.
> >I think it's a case of so called "thread starvation" and would be very glad
> >to know how to avoid it.
> 
> I guess this depends on what you do in "block".  It's difficult to 
> analyze this without having all the information...
> 
> Can you provide more detail?
> 
> Cheers
> 
> 	robert
> 
> -- 
> remember.guy do |as, often| as.you_can - without end
> 

Method do_loading is used for two purposes:
1. loading of a world:
   code in the block goes through a tree of directories and in each reads
   a XML file
2. loading of a level:
   two XML files (level description & map data created in Tiled) + 
   one ruby script (which often requires many others) are loaded from a 
   given directory, many graphics are loaded and huge SDL surfaces are built

Thread starvation usually occurs in the second case.

Jakub

-- 
"Configure complete, now type 'make' and PRAY."

                (configure script of zsnes - www.zsnes.com)