Re: another try at multithreading

[Ignacio Burgueño <ignaciob@...>]

Javier Guerra Giraldez wrote:
> On Tuesday 24 June 2008, Jérôme Vuarand wrote:
> > That is quite an interesting thread, though I'd like to come back to a
> > point that has been discarded too quickly in my opinion.
> >
> > 2008/6/19 Javier Guerra <javier@guerrag.com>:
> > > An obvious improvement might be to use finer locks, maybe one per
> > > mutable object; but a pthread mutex lock weights between 40 and 64
> > > bytes each.  way too much.  readers/writer locks are even bigger.
>
> this days i've been reading about lock implementations, and found this 
> (http://people.redhat.com/drepper/futex.pdf), reimplemented in C i get 4 byte 
> locks, and first tests show that could also work at 1byte.  they're also 
> noticeably faster than pthread locks, especially in the non-contented case 
> (up to 60-70% faster).
>
> the non-contented case is interesting, because since they're totally userspace 
> in this case (only call the kernel if the lock is contented), and using a 
> lock per object means a lot less contentions and higher opportunity for 
> concurrency.


Interesting. It works like critical sections on Windows, but taking 6 
times less space (a CS in Windows takes 24 bytes).

Thanks for the link.