diff options
Diffstat (limited to 'docs/specs')
| -rw-r--r-- | docs/specs/rapl-msr.rst | 25 |
1 files changed, 12 insertions, 13 deletions
diff --git a/docs/specs/rapl-msr.rst b/docs/specs/rapl-msr.rst index 1202ee89be..aaf0db9f91 100644 --- a/docs/specs/rapl-msr.rst +++ b/docs/specs/rapl-msr.rst @@ -9,11 +9,12 @@ The consumption is reported via MSRs (model specific registers) like MSR_PKG_ENERGY_STATUS for the CPU package power domain. These MSRs are 64 bits registers that represent the accumulated energy consumption in micro Joules. -Thanks to the MSR Filtering patch [#a]_ not all MSRs are handled by KVM. Some -of them can now be handled by the userspace (QEMU). It uses a mechanism called -"MSR filtering" where a list of MSRs is given at init time of a VM to KVM so -that a callback is put in place. The design of this patch uses only this -mechanism for handling the MSRs between guest/host. +Thanks to KVM's `MSR filtering <msr-filter-patch_>`__ functionality, +not all MSRs are handled by KVM. Some of them can now be handled by the +userspace (QEMU); a list of MSRs is given at VM creation time to KVM, and +a userspace exit occurs when they are accessed. + +.. _msr-filter-patch: https://patchwork.kernel.org/project/kvm/patch/20200916202951.23760-7-graf@amazon.com/ At the moment the following MSRs are involved: @@ -92,9 +93,12 @@ found by the sysconf system call. A typical value of clock ticks per second is package has 4 cores, 400 ticks maximum can be scheduled on all the cores of the package for a period of 1 second. -The /proc/[pid]/stat [#b]_ is a sysfs file that can give the executed time of a -process with the [pid] as the process ID. It gives the amount of ticks the -process has been scheduled in userspace (utime) and kernel space (stime). +`/proc/[pid]/stat <stat_>`__ is a procfs file that can give the executed +time of a process with the [pid] as the process ID. It gives the amount +of ticks the process has been scheduled in userspace (utime) and kernel +space (stime). + +.. _stat: https://man7.org/linux/man-pages/man5/proc.5.html By reading those metrics for a thread, one can calculate the ratio of time the package has spent executing the thread. @@ -148,8 +152,3 @@ Current Limitations - Only the Package Power-Plane (MSR_PKG_ENERGY_STATUS) is reported at the moment. -References ----------- - -.. [#a] https://patchwork.kernel.org/project/kvm/patch/20200916202951.23760-7-graf@amazon.com/ -.. [#b] https://man7.org/linux/man-pages/man5/proc.5.html |