Intel® VTune™ Amplifier

Memory Access Analysis for Cache Misses and High Bandwidth Issues

Use the Intel® VTune™ Amplifier's Memory Access analysis to identify memory-related issues, like NUMA problems and bandwidth-limited accesses, and attribute performance events to memory objects (data structures), which is provided due to instrumentation of memory allocations/de-allocations and getting static/global variables from symbol information.

How It Works

Memory Access analysis type uses hardware event-based sampling to collect data for the following metrics:

Note

The list of metrics may vary depending on your microarchitecture.

Many of the collected events used in the Memory Access analysis are precise. This simplifies understanding the data access pattern. Off-core traffic is divided into the local DRAM and remote DRAM accesses. Typically, you should focus on minimizing remote DRAM accesses that usually have a high cost.

Configure and Run Analysis

To configure options for the Memory Access analysis:

Prerequisites: Create a project.

  1. Click the (standalone GUI)/ (Visual Studio IDE) Configure Analysis button on the Intel® VTune™ Amplifier toolbar.

    The Configure Analysis window opens.

  2. From HOW pane, click the Browse button and select Memory Access.

  3. Configure the following options:

    CPU sampling interval, ms field

    Specify an interval (in milliseconds) between CPU samples.

    Possible values - 0.01-1000.

    The default value is 1 ms.

    Analyze dynamic memory objects check box (Linux only)

    Enable the instrumentation of dynamic memory allocation/de-allocation and map hardware events to such memory objects. This option may cause additional runtime overhead due to the instrumentation of all system memory allocation/de-allocation API.

    The option is disabled by default.

    Minimal dynamic memory object size to track, in bytes spin box (Linux only)

    Specify a minimal size of dynamic memory allocations to analyze. This option helps reduce runtime overhead of the instrumentation.

    The default value is 1024.

    Evaluate max DRAM bandwidth check box

    Evaluate maximum achievable local DRAM bandwidth before the collection starts. This data is used to scale bandwidth metrics on the timeline and calculate thresholds.

    The option is enabled by default.

    Analyze OpenMP regions check box

    Instrument and analyze OpenMP regions to detect inefficiencies such as imbalance, lock contention, or overhead on performing scheduling, reduction and atomic operations.

    The option is disabled by default.

    Details button

    Expand/collapse a section listing the default non-editable settings used for this analysis type. If you want to modify or enable additional settings for the analysis, you need to create a custom configuration by copying an existing predefined configuration. VTune Amplifier creates an editable copy of this analysis type configuration.

  4. Click the Start button to run the analysis.

Limitations:

View Data

For analysis, explore the Memory Usage viewpoint that includes the following windows:

Support Limitations

Memory Access analysis is supported on the following platforms:

If you need to analyze older processors, you can create a custom analysis and choose events related to memory accesses. However, you will be limited to memory-related events available on those processors. For information about memory access events per processor, see the VTune Amplifier tuning guides.

For dynamic memory object analysis on Linux, the VTune Amplifier instruments the following Memory Allocation APIs:

See Also