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Re: [Qemu-devel] [PATCH] Enabled building of x86_64 code on Mac OS X
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [PATCH] Enabled building of x86_64 code on Mac OS X |
Date: |
Tue, 27 Jan 2009 00:59:20 +0000 |
User-agent: |
KMail/1.9.9 |
On Tuesday 27 January 2009, Jamie Lokier wrote:
> Paul Brook wrote:
> > > Out of curiousity, what are the benefits of using 64-bit apps in OS X?
> >
> > My guess is that same as most other x86 targets: The i386 legacy
> > mode is crippled by lack of registers, modern x86 hardware has a big
> > fat wide memory bus, and noone's bothered implementing an ILP32
> > 64-bit API[1], so 64-bit apps give measurably better overall
> > performance.
>
> Except they use more memory and memory bandwidth (arguably filling
> nearly half of it with zeros most of the time :-) so worse overall
> performance in some cases.
I did say overall performance.
My experience with AMD hardware is that you generally get ~10% overall
improvement from LP64. Intel hardware (particularly the early 64-bit cores)
less so, but it's generally still a win.
I guess ILP32 long mode would probably increase that further, and avoid the
odd regressions. It's an awful lot of work to implement though, especially on
a target that isn't used to having lots of incompatible variants.
Paul
- [Qemu-devel] [PATCH] Enabled building of x86_64 code on Mac OS X, Alexander Graf, 2009/01/24
- Re: [Qemu-devel] [PATCH] Enabled building of x86_64 code on Mac OS X, Anthony Liguori, 2009/01/26
- Re: [Qemu-devel] [PATCH] Enabled building of x86_64 code on Mac OS X, Paul Brook, 2009/01/26
- Re: [Qemu-devel] [PATCH] Enabled building of x86_64 code on Mac OS X, Jamie Lokier, 2009/01/26
- Re: [Qemu-devel] [PATCH] Enabled building of x86_64 code on Mac OS X,
Paul Brook <=
- Re: [Qemu-devel] [PATCH] Enabled building of x86_64 code on Mac OS X, Anthony Liguori, 2009/01/26
- Re: [Qemu-devel] [PATCH] Enabled building of x86_64 code on Mac OS X, Alexander Graf, 2009/01/27
- Re: [Qemu-devel] [PATCH] Enabled building of x86_64 code on Mac OS X, Jamie Lokier, 2009/01/27
- Re: [Qemu-devel] [PATCH] Enabled building of x86_64 code on Mac OS X, Laurent Desnogues, 2009/01/27
Re: [Qemu-devel] [PATCH] Enabled building of x86_64 code on Mac OS X, C . W . Betts, 2009/01/26