January 23rd, 2008
Analysis: Server Side Java energy efficiency versus load
With the arrival of the latest standardized energy efficiency benchmark from SPEC, we have a good way to measure server efficiency. In light of the recent controversy over flawed energy efficiency studies that have unfortunately been touted by so many in the press instead of SPEC, I thought I’d offer some more in-depth analysis on energy efficiency.
The new SPECpower_ssj2008 benchmark gives us a standardized way of measuring energy efficiency for Server Side Java. SPECpower_ssj2008 gives us efficiency data at varying workloads going from 0% to 100% at increments of 10%. Then it provides us with a Performance to Power Ratio curve along with an average efficiency of those 11 workload measurements. The two graphs below are compiled from the SPEC database. It represents the fastest Intel quad-core system (below left) versus the only AMD CPU submitted to the SPECpower_ssj2008 database to date which is a special energy-efficient Opteron 2216HE (below right).
The two graphs above show more than a 3 to 1 advantage for the fastest Intel system when we look at it in terms of percent workload. This is a perfectly valid way of analyzing the data, but the tradeoff is that you’re not seeing the efficiency of each processor at absolute workloads which might be valuable if you need a system with lighter workloads. So to offer an alternative method of interpreting the efficiency data, I plotted out the following Efficiency versus CPU capacity graph with published data from SPEC (and some MS Excel help from analyst David Kanter).
- DP = Dual Processor
- UP = Single Processor (Uni-Processor)
- QC = Quad Core
- DC = Dual Core
- FB = Fully Buffered
- “Operations per joule” is identical to ssj_ops/watt unit used by SPEC.
- “Operations per second” refers to Server Side Java performance.
The blue curve represents the Intel E5450 server shown in the SPEC “Performance to Power” chart above left while the cyan curve represents the AMD 2216HE system. You’ll notice that the curves are somewhat close together at the lower workloads which means the AMD system is almost as efficient as Intel at lighter workloads. But at peak performance levels, Intel is three times faster than the AMD 2216HE system and more then three times the energy efficiency. So if you had to buy three of the AMD 2216HE systems to get the same Server Side Java capacity as the Intel E5450, it would cost you three times the power.
You’ll also notice the pink curve spiking upwards in efficiency just shy of the absolute peak efficiency level of Intel’s latest 45nm E5450 3.0 GHz quad-core CPU. This single-socket single-processor 2.4 GHz XEON X3220 Intel server is by far the most efficient system at lighter workloads. Had a newer single-socket CPU like the 45nm QX9650 3.0 GHz 45nm quad-core processor been used, the efficiency curve would probably fly off this chart. Intel’s 5100 series “San Clemente” chipset will also get much better efficiency than anything on this graph because it uses lower power registered DDR2-667 memory like AMD.
<Next page - How to spot a flawed CPU energy efficient study>
Pages: 1 2
George Ou is Technical Director of ZDNet. See his full profile and disclosure of his industry affiliations.
