System Overview Analysis
Hardware Event-Based Sampling Mode
- Atrace* events: input, view, webview, audio, video, camera, hal, res, dalvik
- Ftrace events: sched, freq, idle, workq, filesystem, irq, softirq, sync, disk
Hardware Tracing Mode (Linux and Android Targets)
- To enable system-level analysis for this mode, consider setting the/proc/sys/kernel/perf_event_paranoidvalue to 0 or less.
- To see the kernel module and its symbols, set/proc/sys/kernel/kptr_restrictto 0.
- Make sure there is a disk space on both target and host systems. Depending on the number of CPU cores, the amount of collected data may reach 1GB per second.
- Make sure your kernel version is 4.3 or higher.
- This mode is available for platforms based on Intel® microarchitectures code named Skylake and newer.
- Analyze user/kernel mode transitions and interrupts
- Explore execution of unexpected processes or system services
- Measure particular stages of workload execution without static instrumentation
- Analyze CPU core activities at the microsecond level
- Analyze a kernel/driver or application module by measuring exact CPU time with a nanosecond precision
- Triage latency issues resulted from:
- changes in the execution code flow
- preemption by another process
- resource sharing issues
- page faults
- power consumption issues caused by unexpected wake-ups
- This analysis requires a direct access to the hardware. It does not work inside a Guest VM.
- In most cases, the collection overhead in this mode is less than 10%. It can be higher if your application is IO or DRAM bound.
- The Hardware Tracing mode does not require sampling drivers.
Configure and Run Analysis
- Click theConfigure Analysisbutton onIntel® VTune™toolbar.ProfilerTheConfigure Analysiswindow opens.
- FromHOWpane, click the Browse button and selectSystem Overview.
- SelectHardware TracingorHardware Event-Based Samplingmode.For theHardware Tracingmode, you can also enable theAnalyze interruptsoption.With the defaultHardware Tracingconfiguration,Intel® VTune™stops the data collection when a 1GB data limit is reached. You can change this limit in theProfilerAdvancedsection of theWHATpane:
- Click the Start button to run the analysis.
Power Usage Analysis
Frequency has dropped below the OS frequency due to assertion of external PROCHOT.
Frequency has dropped below the OS frequency due to a thermal event.
Frequency has dropped below the OS frequency due to a Residency State Regulation Limit violation.
Frequency has dropped below the OS frequency due to a Running Average Thermal Limit violation.
Frequency has dropped below the OS frequency due to electrical or other constraints.
Frequency has dropped below the OS frequency due to package/platform-level power limiting PL1.
Frequency has dropped below the OS frequency due to package/platform-level power limiting PL2/PL3.
Frequency has dropped below the OS frequency due to multi-core turbo limits.
Frequency has dropped below the OS frequency due to turbo transition attenuation. This can cause performance degradation due to frequent changes in operating ratio.