Re: Need kernel patch to compile with Intel compiler

[Matthias-Christian Ott <matthias.christian@tiscali.de>]

Tetsuji "Maverick" Rai wrote:
> On 5/13/05, Chris Friesen <cfriesen@nortel.com> wrote:
>
> > Richard B. Johnson wrote:
> >
> >
> > > The kernel is designed to be compiled with the GNU 'C' compler
> > > supplied with every distribution. It uses a lot of __asm__()
> > > statements and other GNU-specific constructions.
> >
> > Yep.  And Intel added a bunch of them to their compiler so that they
> > could build a kernel with it.
> >
> >
> > > Why would you even attempt to convert the kernel sources to
> > > be compiled with some other tools?
> >
> > The Intel compiler is quite good at optimizing for their processors (and
> > ironically for AMD ones as well).  However, I think that a lot of the
> > gains come from the vectorizer, which of course can't be used with
> > kernel code.
> >
> > Chris
>
>
> Yes, that's why I wanted to use Intel's compiler for kernel (of course
> I didn't mean to use C++; the product's name is C++, it doesn't sell C
> alone.)    Its vectorization is so nice that SETI@home calculates
> 20-30% faster than the original one compiled with gcc.
>
> But I thought it's not such a good idea to build kernel with Intel
> compiler, because kernel's speed doesn't affect so much in my case. 
> And that vectorization isn't so effective in kernel.  PGO (profile
> guided optimization) is the only effective optimization in the kernel
> according to
> http://softwareforums.intel.com/ids/board/message?board.id=16&message.id=1504
>
> So I decided not to try this...looks like too much effort and little
> gain.  and I guess that's why nobody is trying this now.
Yeah that's what the 2.6.5 patch does. Some People talked about 20% more speed with this patch last year. If anyone is 
able to patch the current kernel the patch should be in -mm.

Matthias-Christian Ott
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