Re: [RFC -tip 0/4] x86: reduce fixup of uaccess

Ingo Molnar
2009-01-06T10:09:33Z

* Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> wrote:

> This is my second try to reduce fixup code size for exceptions of uaccess.
>
> This patch series reduces fixup code for exceptions of uaccess in signal.
>
> I gave up to make direct jump to end of function when an exception occurs.
> However, I thought fixup code could be reduced. The concept is that to add
> uaccess_err in thread_info and set it to -EFAULT on exception, finally check
> this value on the last of function.
>
> Is this good to reduce code size?
>
> The code size reductions are below;
> $ size *signal*.o.*
> text data bss dec hex filename
> 4741 0 0 4741 1285 ia32_signal.o.new
> 6006 0 0 6006 1776 ia32_signal.o.old
> 3577 0 0 3577 df9 signal.o.new
> 4540 0 0 4540 11bc signal.o.old
> 3855 0 0 3855 f0f signal32.o.new
> 4876 0 0 4876 130c signal32.o.old

looks very nice! Since kernel execution is i-cache-cold in the typical
case, this will probably transform into a performance improvement as well.

Ingo