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Message-ID: <CAO6sEsCoWpiR+B=GcpQfp1CFiTa2YkoyxEEMezP_Dr2faq-EeQ@mail.gmail.com> Date: Sun, 25 Feb 2018 18:36:49 -0500 From: Pradyumna Kaushik <pkaushi1@...ghamton.edu> To: linux-kernel@...r.kernel.org Subject: Inconsistent values of perfevent hardware counters when measuring power consumption of DRAM using RAPL Hi, I recently noticed a large inconsistency in the data retrieved from the perf_event hardware counters pertaining to the power consumption of DRAM. This inconsistency was noticed upon a kernel upgrade from 4.4.0 to 4.14.20. Machine specs, Dual Socket. Processor specs: Intel(R) Xeon(R) CPU E5-2650 v3, 2.30 GHz (10 cores with 2 threads per core). So, overall it's a 20 core, 40 thread machine. TDP of the machine -- 210 Watts (105 Watts for each Xeon processor) In my research lab, we use performance co-pilot to measure power consumption of the CPU and DRAM through the use of perfevent hardware counters and RAPL. Old results Ubuntu Xenial Kernel Version: 4.4.0 idle power consumption of CPU -- 33.34 Watts idle power consumption of DRAM -- 14.76 Watts New results (after kernel upgrade): Ubuntu Xenial Kernel Version: 4.14.20 Idle power consumption of CPU -- 33.23 Watts Idle power consumption of DRAM -- 59.15 Watts Can anyone give me some insight as to why this is the case? -- Thanks and Regards Pradyumna Kaushik Graduate Student Department of Computer Science Thomas J. Watson School of Engineering and Applied Science Binghamton University
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