PMU – Equivalence
Requirement
1.0 | Use Linux perf interface to collect data about performance events on a per core basis |
|
2.0 | Use jevents library (PMU tools) |
|
3.0 | Report hardware cache events, kernel PMU events, software events, hardware specific events |
|
4.0 | Should have a configurable interval |
|
5.0 | Should have configurable hardware specific events list |
|
6.0 | Provide SNMP support for any collectd values, through an PMU MIB |
|
7.0 |
|
|
Overview
Performance counters are CPU hardware registers that count hardware events such as instructions executed, cache-misses suffered, or branches mispredicted. They form a basis for profiling applications to trace dynamic control flow and identify hotspots. Linux perf interface provides rich generalized abstractions over hardware specific capabilities.
...
The intel_pmu plugin collects information provided by Linux perf interface. Using this interface, the intel_pmu plugin should collect the following metrics:
Name | Type | Type Instance | Description |
| Kernel PMU events | |||
cpu-cycles | counter | cpu-cycles |
|
instructions | counter | instructions |
|
cache-references | counter | cache-references |
|
cache-misses | counter | cache-misses |
|
Branches | counter | Branches |
|
branch-misses | counter | branch-misses |
|
bus-cycles | counter | bus-cycles |
|
| Hardware cache events | |||
L1-dcache-loads | counter | L1-dcache-loads |
|
L1-dcache-load-misses | counter | L1-dcache-load-misses |
|
L1-dcache-stores | counter | L1-dcache-stores |
|
L1-dcache-store-misses | counter | L1-dcache-store-misses |
|
L1-dcache-prefetches | counter | L1-dcache-prefetches |
|
L1-dcache-prefetch-misses | counter | L1-dcache-prefetch-misses |
|
L1-icache-loads | counter | L1-icache-loads |
|
L1-icache-load-misses | counter | L1-icache-load-misses |
|
L1-icache-prefetches | counter | L1-icache-prefetches |
|
L1-icache-prefetch-misses | counter | L1-icache-prefetch-misses |
|
LLC-loads | counter | LLC-loads |
|
LLC-load-misses | counter | LLC-load-misses |
|
LLC-stores | counter | LLC-stores |
|
LLC-store-misses | counter | LLC-store-misses |
|
LLC-prefetches | counter | LLC-prefetches |
|
LLC-prefetch-misses | counter | LLC-prefetch-misses |
|
dTLB-loads | counter | dTLB-loads |
|
dTLB-load-misses | counter | dTLB-load-misses |
|
dTLB-stores | counter | dTLB-stores |
|
dTLB-store-misses | counter | dTLB-store-misses |
|
dTLB-prefetches | counter | dTLB-prefetches |
|
dTLB-prefetch-misses | counter | dTLB-prefetch-misses |
|
iTLB-loads | counter | iTLB-loads |
|
iTLB-load-misses | counter | iTLB-load-misses |
|
branch-loads | counter | branch-loads |
|
branch-load-misses | counter | branch-load-misses |
|
| Software events | |||
cpu-clock | counter | cpu-clock |
|
task-clock | counter | task-clock |
|
context-switches | counter | context-switches |
|
cpu-migrations | counter | cpu-migrations |
|
page-faults | counter | page-faults |
|
minor-faults | counter | minor-faults |
|
major-faults | counter | major-faults |
|
alignment-faults | counter | alignment-faults |
|
emulation-faults | counter | emulation-faults |
|
Plugin configuration
The following configuration options should be supported by intel_pmu collectd plugin:
Name | Description | Comment |
Interval | The interval within which to retrieve statistics on monitored events in seconds | Interval option is supported by collectd and is defined in <LoadPlugin> block. No additional functionality should be developed in intel_pmu plugin to support this option. |
ReportHardwareCacheEvents | Enable/disable monitoring of hardware cache events |
|
ReportKernelPMUEvents | Enable/disable monitoring of kernel PMU events |
|
ReportSoftwareEvents | Enable/disable monitoring of software vents |
|
| EventList | Path to hardware events list file for current CPU. | File can be downloaded by event_download.py script which is part of pmu-tools package. |
HardwareEvents | String containing comma separated list of hardware specific events to monitor |
|
| Cores | Core groups definition. Monitored metrics are reported only for configured cores. If this option is omitted all available cores are monitored. If a group is enclosed in square brackets each core is added individually to a separate group (that is statistics are not aggregated). | Allowed formats: |
Here is an example of the plugin configuration section of collectd.conf file:
<Plugin intel_pmu>
HWCacheEventsReportHardwareCacheEvents true
KernelPMUEventsReportKernelPMUEvents true
SWEventsReportSoftwareEvents true
EventList "/var/cache/pmu/GenuineIntel-6-55-core.json"HWSpecificEvents "L2_RQSTS.CODE_RD_HIT,L2_RQSTS.CODE_RD_MISS,cpl_cycles.ring123" "L2_RQSTS.ALL_CODE_RD"
Cores ""</Plugin>
Implementation details
intel_pmu plugin does not introduce its own layer of functionality. It just reads configuration provided by user and prepares all needed parameters/data structures for jevents API. This table shows the correspondence between plugin’s API and jevents API that is used to configure Linux perf monitoring.
plugin API | jevents API | Description |
pmu_config | | Parse events groups to monitor provided by user in collectd.conf |
pmu_init | resolve_event | Resolve hardware specific events names to perf events (perf_event_attr) |
setup_event | Setup perf events for monitoring | |
pmu_read | read_all_events | Read values of all monitored events |
pmu_shutdown | | |
For more details on plugin API see collectd plugin implementation guide https://collectd.org/wiki/index.php/Plugin_architecture.
...
The following table outlines possible impact(s) the deployment of this deliverable may have on the current system.
Ref | System Impact Description | Recommendation / Comments |
1 |
|
|
Key Assumptions
The following assumptions apply to the scope specified in this document.
Ref | Assumption | Status |
1 |
|
|
Key Exclusions
The following exclusions apply to the scope discussed in this document.
Ref | Exclusion | Status |
1 |
|
|
Key Dependencies
The following table outlines the key dependencies associated with this deliverable.
Ref | Dependency | Status |
1 | libjevents |
|
2 | Net-SNMP |
|
3 |
|
|
4 |
|
|