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Re: [Xen-users] HTPC + DUAL PC In one

  • To: xen-users@xxxxxxxxxxxxx
  • From: Gordan Bobic <gordan@xxxxxxxxxx>
  • Date: Wed, 16 Jul 2014 18:01:49 +0100
  • Delivery-date: Wed, 16 Jul 2014 17:02:43 +0000
  • List-id: Xen user discussion <xen-users.lists.xen.org>

On 2014-07-16 16:01, Austin S Hemmelgarn wrote:
I hadn't thought about this before now, but part of my results may be
because my desktop is running Gentoo with very aggressive optimizations
for the specific processor, whereas the Intel server is running Fedora
20, which just uses -O2 -mtune=generic for optimizations.

Different optimization levels make relatively minor differences. It's
when you switch to a compiler that does vectorization properly (e.g. ICC)
that you see significant performance increases.

factor might be that most of my workloads, and therefore most of the
benchmarking that I do, are memory-bound, and even though both systems
use DDR3-1600 memory, the server is a NUMA system and has the memory
split between the two processors.

That can make a difference, depending on how good the scheduler is
at migrating process to the memory rather than remote accessing
the memory.

Just comparing processors of similar price from AMD and Intel, you will
almost always get a better processor from AMD.  It may not always have
the most up-to date set of ISA extensions, but that hardly matters when
running Windows because Windows won't try to take advantage of anything
that came out after that version of Windows (which is why XP's
performance sucks compared to Win7 on newer systems).

I never noticed this at all. Bloat and feature creep vastly outweighs
relatively marginal benefits from minor ISA extensions. Consider that
x86-64 features SSE (there is no x86-64 CPU that doesn't have SSE),
which makes a big difference _if you use it_ (which most compilers do
a very poor job of), but jumps to SSE2 and further make relatively
little difference). So if you are running XP x64 there is going to be
very little performance from compiler output compared to, say, Windows
7 x64.

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