Intel® VTune™ Amplifier

Driverless Event-Based Sampling Collection

To enable hardware event-based sampling analysis on your platform, the Intel® VTune™ Amplifier can use either sampling drivers that require root privileges for installation on the Linux* and Android* systems or the Perf* utility, which is part of the default VTune Amplifier installation package.

VTune Amplifier runs the hardware event-based sampling analysis in the driverless mode with the Perf utility if:

Note

VTune Amplifier is installed to your default account. For non-root users, it provides a notification during the installation claiming that the sampling driver cannot be installed, so some product features could be limited or unavailable. To have the sampling driver installed, you need to re-start the install process under the root account or contact your administrator.

On Linux, the driverless collection is a default mode for analyses based on hardware event-based sampling with stacks (for example, Hotspots or Threading).

Prerequisites for Driverless Collection

VTune Amplifier can use the driverless Perf-based collection if the following requirements are satisfied:

Driverless Collection Modes

VTune Amplifier supports the following Perf-based collection types:

To configure system-wide driverless collection:

Set the /proc/sys/kernel/perf_event_paranoid value to 0 or less. Root privileges are required.

Note

For the kernel modules resolution, make sure you have enough permissions to read kernel symbols information from the /proc/kallsyms file.

To check the data collection type used for your analysis:

Scroll down to the Collection and Platform Info section in the Summary window and check the Collector Type value:

To use only driverless collection, where possible:

Create a custom analysis and select the Enable driverless collection option.

From the command line, use the -knob enable-driverless-collection=true option. For example:

amplxe-cl -collect-with runsa -knob enable-stack-collection=true -knob stack-size=0 -knob enable-user-tasks=true -knob event-config=CPU_CLK_UNHALTED.THREAD:sa=2000000, INST_RETIRED.ANY:sa=2000000, -knob enable-driverless-collection=true

To disable the driverless collection for your analysis:

Create a custom analysis and set the Stack size option to 0 (unlimited) value.

From the command line, use the -knob stack-size=0 option. For example:

amplxe-cl -collect-with runsa -knob enable-stack-collection=true -knob stack-size=0 -knob enable-user-tasks=true -knob event-config=CPU_CLK_UNHALTED.THREAD:sa=2000000,INST_RETIRED.ANY:sa=2000000
This option disables the Perf driverless collection for stacks and enables the VTune Amplifier driver-based collection instead.

Analysis Limitations

Perf-based driverless collection is applicable to all hardware event-based sampling analysis types, such as Hotspots (hardware event-based sampling mode), Microarchitecture Exploration, and Custom event-based sampling analysis types on Linux and Android OS. If the uncore events support is available on the system, the VTune Amplifier also uses the Perf collection for Memory Access, HPC Performance Characterization, and Microarchitecture Exploration analysis types with the Analyze memory bandwidth option enabled.

The following additional limitations are also possible for the driverless collection:

Note

Run the <install-dir>/bin64/amplxe-self-checker.sh script to explore the analysis type collection abilities of your system. The script output helps recognize limitations and provides advice on fixing them.

See Also