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SpecCpuInt2006 − Energy variation per task
1
Intel Xeon
AMD Opteron
Sparc64 V
0.8
0.6
0.4
0.2
0
FIGURE 12.2
Energy consumption for SPEC CPU 2006 executed in various servers.
counters are a set of special-purpose registers built into modern central pro-
cessing units (CPUs) to store the counts of hardware-related events. Because
they are integrated into the architecture, polling these counters has a negli-
gible overhead in the performance of the workload being profiled. Modern
servers come with a high number of performance counters that can be
polled. By collecting performance counters together with information on the
power consumption of the server, power consumption can be modeled and
thus predicted. Servers are also shipped with a large amount of sensors to
collect temperature, fan speed, or power consumption data. These data can
be gathered via the Intelligent Platform Management Interface (IPMI) tool
(http://ipmitool.sourceforge.net) with negligible overhead. Information of
the performance counters can be correlated with power and then regressed
to obtain a model for dynamic energy. The performance counters that influ-
ence the model vary depending on the system architecture and allow an
explanation for the differences in power consumption of the same workload
in different servers.
12.4.3 Data Center Cooling Power and Data Room Modeling Techniques
In a typical air-cooled data center room, servers are mounted in racks,
arranged in alternating cold/hot aisles, with the server inlets facing cold
air and the outlets creating hot aisles. The computer room air conditioning
(CRAC) units pump cold air into the data room and extract the generated
heat (see Figure 12.3).
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