docs/specs/rapl-msr.rst

6 energy consumption of various power domains (e.g. CPU packages, DRAM, etc.).
13 not all MSRs are handled by KVM. Some of them can now be handled by the
14 userspace (QEMU); a list of MSRs is given at VM creation time to KVM, and
28 The ``*_POWER_UNIT``, ``*_POWER_LIMIT``, ``*_POWER INFO`` are part of the RAPL
29 spec and specify the power limit of the package, provide range of parameter(min
30 power, max power,..) and also the information of the multiplier for the energy
35 The MSR_PKG_ENERGY_STATUS is a counter; it represents the total amount of
39 the consumption of the package. This counter is supposed to overflow at some
45 core that belongs to PKG-0 will not be able to get the value of PKG-1 and
51 In order to update the value of the virtual MSR, a QEMU thread is created.
54 1. Snapshot of the time metrics of all QEMU threads (Time spent scheduled in
57 2. Snapshot of the actual MSR_PKG_ENERGY_STATUS counter of all packages where
63 4. Repeat 2. and 3. and calculate the delta of every metrics representing the
69 6. Retrieve the topology of the Virtual Machine. This helps identify which
73    of vcpu threads so that each vcpu thread will get an equal part of the
76 8. Calculate the ratio of energy spent per vcpu threads.
90 dividing the time in clock ticks. The number of clock ticks per second can be
91 found by the sysconf system call. A typical value of clock ticks per second is
92 100. So a core can run a process at the maximum of 100 ticks per second. If a
94 of the package for a period of 1 second.
97 time of a process with the [pid] as the process ID. It gives the amount
98 of ticks the process has been scheduled in userspace (utime) and kernel
103 By reading those metrics for a thread, one can calculate the ratio of time the
108 A 4 cores package can schedule a maximum of 400 ticks per second with 100 ticks
110 on this package, that means my thread has been scheduled for 1/4 of the whole
111 package. With that, the calculation of the energy spent by the thread on this
112 package during this whole second is 1/4 of the total energy spent by the
130 The qemu-vmsr-helper is working very much like the qemu-pr-helper. Instead of