Developer Guide

  • 2021.1
  • 11/03/2021
  • Public
Contents

Select a Cache Partitioning Preset

Intel recommends those experimenting with software SRAM or cache partitioning to start by using the presets included in the cache configurator tool. Presets are designed to cover the majority of use cases. You can also use the cache configurator to further refine the configuration as needed.
In general, the presets partition the cache to:
  • Establish isolated cache regions dedicated to real-time workloads
  • Restrict the GPU from accessing the entire L3 cache, and avoid overlap with cache partitions dedicated to real-time workloads
  • Dedicate a small portion of the cache for low-latency I/O
Some presets also include software SRAM in the L3 cache, while others also include software SRAM in a subset of the L2 caches.
If you have completed the steps in the Get Started Guide, you applied Preset 4 to your system.
Once a cache partitioning scheme has been applied (either from a preset or custom partitioning scheme), if the partition scheme included any isolated cache regions for real-time workloads then the system administrator needs to set the appropriate Class of Service on the core running the real-time workload. For details, see Allocate Classes of Service to Cores.
If users are attempting to partition the cache on their own without referencing any of the provided presets, Intel recommends reserving software SRAM first (see Reserve Software SRAM) prior to partitioning the remaining cache resources.

Steps

The current cache configuration and software SRAM buffers will be overwritten by the selected preset.
To select a preset:
  1. If you have not already done so, launch the tool as described in Launch the Cache Configurator.
  2. At tool launch, select
    P
    :
    Would you like to add (A) or delete (D) a cache allocation? Or would you like to change the way the configuration is partitioned? (P) P
  3. At the prompt, select one of the presets. For details, see Preset Summary. If you want to exit this screen without selecting any preset, press
    U
    .
  4. The selected preset will overwrite the current configuration. All changes before this will be overwritten. After selecting a preset, enter
    Y
    to apply the configuration and go to the reboot screen. You can check the resulting configuration. If it suits you, enter
    Y
    . You can continue configuration editing by entering
    C
    . To cancel applying the preset, enter
    U
    .
  5. Presets include dedicated cache for real-time workloads. After applying the new partitioning scheme and rebooting into it, you will need to take additional steps outside the cache configurator to allow your real-time application to use the dedicated cache. For details, see Allocate Classes of Service to Cores.
  6. After use, enable RTCM to allow the cache allocation library to work properly. You can enable RTCM with the following commands:
    /usr/share/tcc_tools/scripts/setup_ssram/control_rtcm.sh enable reboot

Product and Performance Information

1

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