Carl Johnson put forth on 1/13/2011 11:34 AM: > Processors Time (seconds) > P1 66 > P2 36 > P3 25 > P4 20 > P5 20 > P6 20 > P7 20 > P8 20 > > I am sure the time would have increased if the system had run out of > memory and had to start swapping. The system is not completely idle > since I am running a KDE 4.4.5 desktop and VirtualBox with two guest > OSs (Debian and NetBSD). I suspect it would have closer to linear > scaling if the system had been completely idle.
Your numbers bear out exactly what I predicted. Look at the decrease in run time from 1 to 2, 2 to 3, and from 3 to 4 processes: #CPUs Decremental run time Fractional gain per CPU 2 30s 1/2 3 11s 1/6th 4 5s 1/13th You can clearly see the effects of serious memory contention when 3 cores are pegged. Bringing the 4th core into the mix yields almost nothing compared to three cores, cutting only 5 seconds from a 66 second run time. I'm anxious to see someone's results for a Phenom II X2 with the 6MB L2 cache to verify my prediction there. That's a tougher prediction though as I haven't modeled the cache behavior of Imagemagick's convert program. And the data above shows it seems to be very memory b/w heavy. Such a test would definitely be very revealing of the effectiveness of the Phenom II X2's L3 cache, given what we've seen so far. -- Stan -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4d30d0f0.7000...@hardwarefreak.com
