Re: [boost] [context review] Several Questions

Subject: Re: [boost] [context review] Several Questions
From: Artyom (artyomtnk_at_[hidden])
Date: 2011-03-21 16:02:13

Hello,

> > > > > sched_yield(): 2108 cycles

> > > > >  ucontext_t:     1795  cycles
> > > > >  fcontext_t:     156 cycles
> > > > > 
> > > 
> > > > Actually it is quite consistent with what you had  show,
> > > > the  Boost.Context is better (but not  significantly) then
> > > > real OS (kernel)  context  switch.
> > > 
> > > factor 13x ?
> > > 
> > 
> > I  was talking about _default_ build which uses ucontext.
> 
> OK - ucontext does  system calls which are time consuming.
> 

Ok I understand and actually I see several things I already would
like to try with Boost.Context.

Let's continue...
-----------------

Several problems I see:

a) (BIG ONE) The shared object link using fcontext crashes!

   Using boost_1_46_0

   Building boost_context:

   bjam toolset=gcc context-impl=asm architecture=x86 instruction-set=native 
address-model=64 --with-context
       variant=release stage

   Then I compile example link.cpp 

   Run it

   It crashes!

   When linking with static libboost_context.a it works...

   OS: Linux artik-laptop 2.6.35-24-generic #42-Ubuntu SMP Thu Dec 2 02:41:37 
UTC 2010 x86_64 GNU/Linux
   Compiler: gcc-4.4.5
   CPU: Intel(R) Core(TM) i5 CPU       M 460  @ 2.53GHz

b) Building with fcontext is... Too complicated

   Options: context-impl=asm architecture=x86 instruction-set=native 
address-model=64

   Why should I specify all these parameters? They should be fully 
auto-configured.

   I understand that BBv2 is far from being too friendly and powerful system
   I still expect that most of parameters should be defined by default
   otherwise there is no chance that users would be actually able to build
   it clearly.

Other Questions
----------------

1. Please provide a rationale why not both methods are compiled to same library?

   Sometimes wouldn't it be better to have option about the type of the method
   you actually use especially if user may want to have both methods.

2. Why boost::contexts::context is template class? How does it benefit from 
this?

   Please provide rationale.

Thanks,
  Artyom