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Stephane Eranian authored
This patch adds a new uncore PMU to expose the Intel RAPL energy consumption counters. Up to 3 counters, each counting a particular RAPL event are exposed. The RAPL counters are available on Intel SandyBridge, IvyBridge, Haswell. The server skus add a 3rd counter. The following events are available and exposed in sysfs: - power/energy-cores: power consumption of all cores on socket - power/energy-pkg: power consumption of all cores + LLc cache - power/energy-dram: power consumption of DRAM (servers only) For each event both the unit (Joules) and scale (2^-32 J) is exposed in sysfs for use by perf stat and other tools. The files are: /sys/devices/power/events/energy-*.unit /sys/devices/power/events/energy-*.scale The RAPL PMU is uncore by nature and is implemented such that it only works in system-wide mode. Measuring only one CPU per socket is sufficient. The /sys/devices/power/cpumask file can be used by tools to figure out which CPUs to monitor by default. For instance, on a 2-socket system, 2 CPUs (one on each socket) will be shown. All the counters measure in the same unit (exposed via sysfs). The perf_events API exposes all RAPL counters as 64-bit integers counting in unit of 1/2^32 Joules (about 0.23 nJ). User level tools must convert the counts by multiplying them by 2^-32 to obtain Joules. The reason for this is that the kernel avoids doing floating point math whenever possible because it is expensive (user floating-point state must be saved). The method used avoids kernel floating-point usage. There is no loss of precision. Thanks to PeterZ for suggesting this approach. To convert the raw count in Watt: W = C * 2.3 / (1e10 * time) or ldexp(C, -32). RAPL PMU is a new standalone PMU which registers with the perf_event core subsystem. The PMU type (attr->type) is dynamically allocated and is available from /sys/device/power/type. Sampling is not supported by the RAPL PMU. There is no privilege level filtering either. Signed-off-by: Stephane Eranian <eranian@google.com> Reviewed-by: Maria Dimakopoulou <maria.n.dimakopoulou@gmail.com> Reviewed-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: acme@redhat.com Cc: jolsa@redhat.com Cc: zheng.z.yan@intel.com Cc: bp@alien8.de Link: http://lkml.kernel.org/r/1384275531-10892-4-git-send-email-eranian@google.comSigned-off-by: Ingo Molnar <mingo@kernel.org>
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