User Guide

Intel® VTune™ Profiler User Guide

ID 766319
Date 11/07/2023
Public

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Document Table of Contents

knob

Set configuration options for the specified analysis type or collector type.

GUI Equivalent

Configure Analysiswindow > HOW pane

Syntax

-knob | -k <knob-name>=<knob-value>

Arguments

knob-name

An analysis type or collector type may have one or more configuration options (knobs) that provide additional instructions for performing the specified type of analysis. To use a knob, you must specify the knob name and knob value.

Multiple knob options are allowed and can be followed by additional action-options, as well as global-options, if needed.

knob-value

There are values available for each knob. In most cases this is a Boolean value, so for Boolean knobs, specify <knob-name>=true to enable the knob.

NOTE:

Knob behavior may vary depending on the analysis type or collector type.

<knob-name>

Description

accurate-cpu-time-detection=true | false (Windows only)

Default: true

Collect more accurate CPU time data. This option requires additional disk space and post-processing time. Administrator privileges are required.

Supported analysis: runss

analyze-loops=true | false

Default: false

Extend loop analysis to collect advanced loops information such as instruction set usage and display analysis results by loops and functions.

Supported analysis: runss, runsa

analyze-mem-objects=true | false

Default: false

Enable the instrumentation of memory allocation/de-allocation and map hardware events to memory objects. This option is supported only for Linux targets which run on the Intel microarchitectures code named Haswell (or newer).

Supported analysis: memory-access

analyze-openmp=true | false

Default: true for the HPC Performance Characterization analysis; false for other analysis types.

Instrument the OpenMP* runtimes in your application to group performance data by regions/work-sharing constructs and detect inefficiencies such as imbalance, lock contention, or overhead on performing scheduling, reduction, and atomic operations. Using this option may cause higher overhead and increase the result size.

Supported analysis: hotspots, threading, hpc-performance, memory-access, uarch-exploration, runsa

analyze-persistent-memory=true | false

Default: false

Collect performance information for Intel® Optane™ Persistent Memory modules.

Supported analysis: platform-profiler

Actions Modified

collect, collect-with

Description

Use the knob action-option to configure knob settings for a collect (predefined analysis types) or collect-with (custom analysis types) action where the analysis type supports one or more knobs. Each analysis type or collector type supports a specific set of knobs, and each knob requires a value. In most cases the knob value is Boolean, so you would use True to enable the knob.

To see all knobs available for a predefined analysis type:

vtune -help collect <analysis_type>

To see knobs for a custom analysis type:

vtune -help collect-with <analysis_type>

Example

This example returns a list of knobs for the Threading analysis type:

vtune -help collect threading

This example runs a custom event-based sampling data collection on an Android system enabling collection of Android framework and chipset events.

vtune -collect-with runss -target-system=android -knob sampling-interval=2 -knob cpu-samples-mode=stack -knob ftrace-config=gfx,dalvik -knob chipset-event-config="GMCH_PARTIAL_WR_DRAM.ANY,GMCH_CORE_CLKS" --target-process com.intel.tbb.example.tachyon

This example configures and runs a custom event-based sampling data collection with the stack size limited to 8192 bytes:

vtune -collect-with runsa -knob enable-stack-collection=true -knob stack-size=8192 -knob enable-call-counts=true -knob event-config=CPU_CLK_UNHALTED.REF_TSC:sa=1800000,CPU_CLK_UNHALTED