Intel® VTune™ Profiler User Guide

User Guide

Contents

Analyze Interrupts

If you configured your collection to monitor IRQ Ftrace* events either by using the System Overview analysis type or custom analysis, the
Intel® VTune™
Profiler
 analyzes code performance inside IRQs and displays interrupts statistics in the default Hardware Events viewpoint. Follow the steps below to analyze the collected interrupt data:

Prerequisites

Analysis of interrupts requires access to the Linux Ftrace subsystem in
/sys/kernel/debug/tracing
. Typically, it is only accessible for the root user.
To analyze interrupts, either run the analysis as root, or edit permissions for
/sys/kernel/debug/tracing
 as described in the Limitations section of the Linux* and Android* Kernel Analysis topic.

Identify Critical Interrupt Handlers

Start your analysis with the
Summary
 window that provides overall interrupt handlers statistics in the following sections:
  • Top Interrupt Handlers
     that shows the most active interrupt handlers sorted by Interrupt Time.
    Top Interrupt Handlers
    Clicking an interrupt handler in the list opens the grid view grouped by
    Interrupt/Interrupt Duration Type/Function/Call Stack
     level.
  • Interrupt Duration Histogram
     that shows a distribution of interrupt handler instances per duration types defined by the
    VTune
    Profiler
    . High number of slow instances may signal a performance bottleneck. Use the drop-down menu to view data for different interrupt handlers.
    Interrupt Duration Histogram
When you identified a slow interrupt in the
Summary
 window, you may switch to the
Event Count
 tab sorted by the
Interrupt/..
 level, locate this interrupt, expand the hierarchy to view a function where slow interrupts occurred, and double-click the function to explore its source code in the Source view.

Analyze Slow Interrupts on the Timeline

Switch to the
Platform
 tab in the
Hardware Events
 viewpoint to analyze CPU utilization, GPU usage and power consumption during your code execution and correlate this data with the time frames when slow interrupts occurred. You may enable the
Slow Interrupts
 markers on the timeline, select a time frame with slow interrupts and zoom in to the selected region for detailed analysis:
System Overview: Interrupts Analysis

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.