Fwd: 5-STABLE kernel build with icc broken

[Peter Jeremy]

On Mon, 2005-Mar-28 23:23:19 -0800, David Leimbach wrote:
>meant to send this to the list too... sorry
>> Are you implying DragonFly uses FPU/SIMD?  For that matter does any kernel?
>
>I believe it does use SIMD for some of it's fast memcopy stuff for
>it's messaging system
>actually.  I remember Matt saying he was working on it.
>
>http://leaf.dragonflybsd.org/mailarchive/kernel/2004-04/msg00262.html

That's almost a year ago and specifically for the amd64.  Does anyone
know what the results were?

>If you can manage the alignment issues it can be a huge win.

For message passing within the kernel, you should be able to mandate
alignment as part of the API.

I see the bigger issue being the need to save/restore the SIMD
engine's state during a system call.  Currently, this is only saved on
if a different process wants to use the SIMD engine.  For MMX, the
SIMD state is the FPU state - which is non-trivial.  The little
reading I've done suggests that SSE and SSE2 are even larger.

Saving the SIMD state would be more expensive that using integer
registers for small (and probably medium-sized) copies.

-- 
Peter Jeremy