[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: 64-bit Kernel Question



On Mon, 2009-03-09 at 20:22 -0400, Tom Lane wrote:
> "Patrick O'Callaghan" <pocallaghan gmail com> writes:
> > On Mon, 2009-03-09 at 12:49 -0700, Adam Williamson wrote:
> >> The most common CPU-bound operation in our world, I guess, is
> >> compilation, and you would notice a definite improvement in speed there,
> >> running x86-64 vs x86-32 - not huge, but noticeable. Certain database
> >> and I think scientific operations that are CPU-bound also derive a
> >> significant benefit. It depends on whether the code can take advantage
> >> of much bigger registers, AIUI.
> 
> > Anyone who does even casual video processing (e.g. with transcode
> > filters) definitely will notice. This is something that pegs both cores
> > to 100% when I run it, until the fan kicks in and it slows a bit.
> 
> It's not so much about *bigger* registers as *more* registers.  The
> x86 architecture is incredibly register-starved (what comes of being
> bug-compatible with a 1971 CPU design...).  When AMD did the x86_64
> redesign they took advantage of the opportunity to define a more
> reasonable number of registers.  Avoiding swapping values in and out
> to memory all the time is a large chunk of the reason for the
> performance boost in x86_64 code.  It's not uncommon for x86_64
> code to be physically smaller than comparable x86 code because of
> elimination of those extra instructions, even though the individual
> instructions tend to be wider.
> 
> But I agree that a lot of people seldom do anything CPU-intensive
> enough to notice.

Video encoding is also one of the few things that may get a boost from
the post-i586 instruction set enhancements (MMX, SSE, 3DNow!, all that
crap), which can't be used in i586 packages but are used in x86-64
packages, as all x86-64 CPUs support them so it's safe.

And yeah, Patrick, media encoding is probably the *second* most common
high-CPU-use scenario in our world :) It's probably the most common
scenario in the general set of computer users, actually. That's why
Intel is forever harping on it in commercials.
-- 
Adam Williamson
Fedora QA Community Monkey
IRC: adamw | Fedora Talk: adamwill AT fedoraproject DOT org
http://www.happyassassin.net


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]