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Copyright © 2023 The Khronos Group Inc.

Copyright © 2023 Nvidia Corporation.

VK_LAYER_KHRONOS_memory_decompression

The VK_LAYER_KHRONOS_memory_decompression extension layer implements the VK_NV_memory_decompression extension. By default, it will disable itself if the underlying driver provides the extension.

Requirements for the layer

VK_LAYER_KHRONOS_memory_decompression requires an implementation to support the following:

  • VkPhysicalDeviceSubgroupProperties::supportedStages must include VK_SHADER_STAGE_COMPUTE_BIT

  • VkPhysicalDeviceSubgroupProperties::supportedOperations must include VK_SUBGROUP_FEATURE_BASIC_BIT

  • VkPhysicalDeviceVulkan12Features::shaderInt8 feature must be supported and enabled

  • VkPhysicalDeviceVulkan12Features::bufferDeviceAddress feature must be supported and enabled

Configuring the memory_decompression Layer

For an overview of how to configure layers, refer to the Layers Overview and Configuration document.

The memory_decompression Layer settings are documented below.

The memory_decompression Layer can also be enabled and configured using vkconfig. See the vkconfig documentation for more information.

Enabling the Layer

Desktop (Linux/Windows/MacOS)

You must add the location of the generated VK_LAYER_KHRONOS_memory_decompression.json file and corresponding VK_LAYER_KHRONOS_memory_decompression library to your VK_LAYER_PATH in order for the Vulkan loader to be able to find the layer.

Then, you must also enable the layer in one of two ways:

  • Directly in your application using the layer's name during vkCreateInstance
  • Indirectly by using the VK_INSTANCE_LAYERS environment variable.

Setting the VK_LAYER_PATH

Windows

If your source was located in: C:\my_folder\ExtensionLayer and your build folder was build64, then you would add it to the layer path in the following way:

set VK_LAYER_PATH=C:\my_folder\ExtensionLayer\build64\layers\Debug;%VK_LAYER_PATH%

Linux/MacOS

If your source was located in: /my_folder/ExtensionLayer and your build folder was build, then you would add it to the layer path in the following way:

export VK_LAYER_PATH=/my_folder/ExtensionLayer/build/layers:$VK_LAYER_PATH

Forcing the layer with VK_INSTANCE_LAYERS

To force the layer to be enabled for Vulkan applications, you can set the VK_INSTANCE_LAYERS environment variable in the following way:

Windows

set VK_INSTANCE_LAYERS=VK_LAYER_KHRONOS_memory_decompression

Linux/MacOS

export VK_INSTANCE_LAYERS=VK_LAYER_KHRONOS_memory_decompression

To force the layer to be enabled for Vulkan applications, even though the Vulkan implementation supports VK_NV_memory_decompression extension, you can set the VK_MEMORY_DECOMPRESSION_FORCE_ENABLE environment variable in the following way:

Windows

set VK_MEMORY_DECOMPRESSION_FORCE_ENABLE=true

Linux/MacOS

export VK_MEMORY_DECOMPRESSION_FORCE_ENABLE=true



Android

Packaging layer with application

This layer should not require your application to need any additional permissions.

At vkCreateInstance time add the layer

// std::vector<const char *> instance_layers
instance_layers.push_back("VK_LAYER_KHRONOS_memory_decompression");

VkInstanceCreateInfo info;
info.enabledLayerCount = static_cast<uint32_t>(instance_layers_.size());
info.ppEnabledLayerNames = instance_layers_.data();

For this to work libVkLayer_khronos_memory_decompression.so needs to be packaged inside the APK as Android will be able to read in the layer from there. One can open the APK in Android Studio to verify the binary is there. Make sure to match up the correct ABI as well (armeabi-v7a, arm64-v8a, etc).

Globally Enabling the Layer

This will require a debugable application or additional permissions. For more information please read the Android Developer page

Use ADB to enable the layer for your project by:

adb shell "setprop debug.vulkan.layers 'VK_LAYER_KHRONOS_memory_decompression'"

When done, disable the layer using:

adb shell "setprop debug.vulkan.layers ''"



Settings Priority

If you have a setting defined in both the Settings File as well as an Environment Variable, the Environment Variable value will always override the Settings File value. This is intended to let you dynamically change settings without having to adjust the Settings File.



Applying Environment Settings on Android

On Android, you must use properties to set the environment variables. The format of the properties to set takes the following form:

debug. + (lower-case environment variable with 'vk_' stripped)

The easiest way to set a property is from the ADB shell:

adb shell "setprop <property_name> '<property_value>'"

For example:

To set force enable, which on desktop uses VK_MEMORY_DECOMPRESSION_FORCE_ENABLE set the following property:

debug.vulkan.memory_decompression.force_enable

Which you can set in the following way:

adb shell "setprop debug.vulkan.memory_decompression.force_enable true"



Layer Options

The options for this layer are specified in VkLayer_khronos_memory_decompression.json.