DragonFly BSD
DragonFly kernel List (threaded) for 2003-11
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Re: AMD64 impressions (Re: AMD64 box)

From: David Rhodus <drhodus@xxxxxxxxx>
Date: Fri, 7 Nov 2003 13:51:49 -0500

On Nov 7, 2003, at 5:48 AM, Matthew Dillon wrote:
	The best comparison is the AMD box verse the P4 box.  Both are UP
	boxes.  The AMD box is 2.1x faster then the P4 box.  If clock speeds
	scaled, that would make the AMD box equivalent to 2.6GHz P4.  Since
	clock speeds don't scale, the AMD box is more like a 3.3GHz P4.
From most of my timing, the AMD 1.4ghz comes in around equivalent to my
P4 3.06ghz from buildworld timing. Also most of the numbers are a lot
lower on the AMD side as far as memory operations and context switches
which seems like a big benefit.

(2) The AMD's syscall overhead is very low compared to the P4. I ran the 'sc1' test in /usr/src/test/sysperf. The AMD box comes back at 242nS/loop while the P4 takes 1300nS/loop and the DELL box (LEAF/SMP) takes 617nS/loop.

getuid() 0.916s 2402600 loops = 0.381uS/loop on my AMD 1.4ghz.

I think big reason for the speed improvement here is because on every
syscall entry on a P4 you hit a branch misprediction and the AMD it cares
more about just blowing through the instructions which makes it a lot faster
at most things.


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