Processor Scalability and Linux

[Robert Myers]

On Sun, Aug 8, 2010 at 11:12 AM, Joshua C. <joshuacov at googlemail.com> wrote:
> Hi,
>
> I’ve been planning on buying a new machine but I’m not that sure what to take.
>
> We’ve been seeing test and reviews on the internet between amd and
> linux. I can say that when it comes to pure (single) core apps then
> intel might have the lead. When it comes to scalability then amd is on
> the move. You can check some recent reviews between i5–750/760 and
> 1055t/1090t for this. I DO NOT want to start a one–is–better
> discussion here.
>
> We know that in the windows world most of the apps aren’t optimized
> for multicore processers. I think the windows OS isn’t optimized
> either. Therefore the discussion goes down to “what are you going to
> do with it? If you work with video (photoshop) then amd, else  – maybe
> intel”.
>
> However I want to ask how well linux scales on multicore processors. I
> know that maybe more that 90% of all internet servers are running with
> some version of linux. But this doesn’t mean that linux scales better
> than windows, because maybe the costs are at play here – Free (as in
> Freedom) vs. $$. Most of the linux apps are compiled with GCC 4.xx.
> Therefore it goes down to how well GCC is optimized for a multicore
> processor.
>
> My machine also must satisfy some other criteria:
>
> 1.) future–proof (that’s why an amd 6–core ???)

You're apparently not interested in running virtual machines.
Otherwise, you might be more interested in the number of threads as
opposed to the number of cores.  It's not all that hard, these days,
to overcommit even 6 threads (or 8, for that matter).  Unless you are
virtualizing heavily-used servers, it's the ability to carrry distinct
contexts, not execution resources, that limit the ability to
virtualize multiple machines without experiencing noticeable
performance degradation.

Virtualizing Linux on Windows using free software from vmware looks
like the better bet than using wine these days.  No dual boot or funny
fiddling.  Of course, if you're not interested in running virtual
machines, then you're not interested.

The benchmarks you see so often today for multiple cores are only the
ones that are most easily available and don't necessarily reflect any
kind of realistic future.

As to Linux and virtualizing, I'm waiting for a dom0 from Fedora.

> 2.) must be environmental friendly (less watts) (that’s why an intel)

Whatever you buy now will be out of date in a year.

> 3.) good linux support (I’ll put intel here because I think their
> overall support is better than amd. Remember the SB850 and how fast
> amd responded? What about ati?)
>
It seems like most of the problems are with graphics card support and
maybe chipsets, not so much a processor issue.

> Therefore I’m asking if a 6–core amd makes more sense in linux than in
> windows? How well does linux scales?
>

Why would you think Windows scales poorly?  My experience using vmware
under Windows has been very positive with multiple virtual machines
running.  Among other things, I can run multiple versions of Windows
(including XP for legacy) and Linux at the same time.

Robert.