Roman Zippel wrote:
>
> Hi,
>
> On Mon, 11 Feb 2002, David S. Miller wrote:
>
> > It keeps your platform the same, and it does help other platforms.
> > It is the nature of any abstraction change we make in the kernel
> > that platforms have to deal with.
>
> Of what "abstraction change" are you talking about?
> Any change should usually help most architectures and so far the
> thread_info change has only be done a few.
>
> > 2) pointer dereference causes performance problems
> >
> > ummm no, not really, go test it for yourself if you don't
> > believe me
> >
> > This only leaves "I don't want to do the conversion because it has
> > no benefit to ia64." Well, it doesn't hurt your platform either,
> > so just cope :-)
>
> That's simply not true. An extra load might be cheap, maybe on sparc it's
> even free, but on most architectures it has a cost. Additionally every
> access to current requires an extra load, so every function which uses
> current will be larger, all embedded targets will thank you for that.
> Where is the problem to allow these two implementations:
> 1.
> #define current_thread_info() asm(...)
> #define current current_thread_info()->task
> 2.
> #define current asm(...)
> #define current_thread_info() ¤t->thread_info
...or number 3, do a conversion to 2.5.4 thread_info then embed the task
structure inside struct thread_info, like what was just done with VFS
inodes. (embedding the general struct in the arch-specific struct would
make sense to me, whereas I can definitely see how embedding the
arch-specific struct in the general struct would be annoying)
Jeff
-- Jeff Garzik | "I went through my candy like hot oatmeal Building 1024 | through an internally-buttered weasel." MandrakeSoft | - goats.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Fri Feb 15 2002 - 21:00:48 EST