Re: cvs commit: src/lib/libthread_xu Makefile pthread.map src/lib/libthread_xu/arch Makefile.inc src/lib/libthread_xu/arch/alpha Makefile.inc src/lib/libthread_xu/arch/alpha/alpha pthread_md.c src/lib/libthread_xu/arch/alpha/include pthread_md.h src/lib/libthread_xu/arch/amd64 ...

[davidxu <davidxu@xxxxxxxxxxx>]

Joerg Sonnenberger wrote:
> On Tue, Feb 01, 2005 at 03:14:47PM -0800, Matthew Dillon wrote:
>
> > :This is an optimisation for the intra-program switch if you want to call it so.
> > :I would argue that the normal switch case is either user -> kernel or to
> > :a different kernel thread.
> >
> >    You pretty much always want to have just a single page table with a
> >    threaded program.  The %cr3 optimization is a nice plus, but it isn't
> >    why the page table is being shared.  The page table is being shared
> >    because trying to build a threaded program WITHOUT sharing the page
> >    table is extremely expensive.  Every time you'd allocate memory or map
> >    something it would have to be replicated across N page tables.  
> >    Performance would be destroyed.
>
>
> But you can still share most parts of the page table, if you exploit
> the two level approach.
Yes, you can rewrite a pte, but an invlpg intruction is very expensive!
remember you have to operate TLB, which should be avoided in most time.

> Joerg
>
>
> > 						-Matt