Entries for tag "vulkan", ordered from most recent. Entry count: 20.
# Memory management in Vulkan and DX12: slides are online
Slides from my talk at Game Developers Conference (GDC) 2018: "Memory management in Vulkan and DX12" are now available online, as part of materials from Advanced Graphics Techniques Tutorial. Access to this PDF is open to anyone, not behind GDC Vault paywall. I've put some additional information in "backup" slides at the end that I didn't show during my presentation. The slides are designed the way that you can learn from them even without seeing the talk.
Update 2018-05-04: Slides from my talk in PPTX format with additional notes are now available (together with many other GDC 2018 presentations) on page: GDC 2018 Presentations - GPUOpen.
# Debugging Vulkan driver crash - equivalent of NVIDIA Aftermath
New generation, explcit graphics APIs (Vulkan and DirectX 12) are more efficient, involve less CPU overhead. Part of it is that they don't check most errors. In old APIs (Direct3D 9, OpenGL) every function call was validated internally, returned success of failure code, while driver crash indicated a bug in driver code. New APIs, on the other hand, rely on developer doing the right thing. Of course some functions still return error code (especially ones that allocate memory or create some resource), but those that record commands into a command buffer just return
void. If you do something illegal, you can expect undefined behavior. You can use Validation Layers / Debug Layer to do some checks, but otherwise everything may work fine on some GPUs, you may get incorrect result, or you may experience driver crash or timeout (called "TDR"). Good thing is that (contrary to old Windows XP), crash inside graphics driver doesn't cause "blue screen of death" or machine restart. System just restarts graphics hardware and driver, while your program receives
VK_ERROR_DEVICE_LOST code from one of functions like
vkQueueSubmit. Unfortunately, you then don't know which specific draw call or other command caused the crash.
NVIDIA proposed solution for that: they created NVIDIA Aftermath library. It lets you (among other things) record commands that write custom "marker" data to a buffer that survives driver crash, so you can later read it and see which command was successfully executed last. Unfortunately, this library works only with NVIDIA graphics cards and only in D3D11 and D3D12.
I was looking for similar solution for Vulkan. When I saw that Vulkan can "import" external memory, I thought that maybe I could use function
vkCmdFillBuffer to write immediate value to such buffer and this way implement the same logic. I then started experimenting with extensions: VK_KHR_get_physical_device_properties_2, VK_KHR_external_memory_capabilities, VK_KHR_external_memory, VK_KHR_external_memory_win32, VK_KHR_dedicated_allocation. I was basically trying to somehow allocate a piece of system memory and import it to Vulkan to write to it as Vulkan buffer. I tried many things:
HeapAlloc and other ways, with various flags, but nothing worked for me. I also couldn't find any description or sample code of how these extensions could be used in Windows to import some system memory as Vulkan buffer.
Everything changed when I learned that creating normal device memory and buffer inside Vulkan is enough! It survives driver crash, so its content can be read later via mapped pointer. No extensions required. I don't think this is guaranteed by specification, but it seems to work on both AMD and NVIDIA cards. So my current solution to write makers that survive driver crash in Vulkan is:
VkDeviceMemoryfrom memory type that has
HOST_VISIBLE + HOST_COHERENTflags. (This is system RAM. Spec guarantees that you can always find such type.)
vkMapMemoryto get raw CPU pointer to its data.
VK_BUFFER_USAGE_TRANSFER_DST_BITand bind it to that memory using
vkCmdFillBufferto write immediate data with your custom "markers" to the buffer.
VK_ERROR_DEVICE_LOST), read data under the pointer to see what marker values were successfully written last and deduce which one of your commands might cause the crash.
There is also a new extension available on latest AMD drivers: VK_AMD_buffer_marker. It adds just one function:
vkCmdWriteBufferMarkerAMD. It works similar to beforementioned
vkCmdFillBuffer, but it adds two good things that let you write your markers with much better granularity:
vkCmdFillBuffermust be called outside render pass.
I created a simple library that implements all this logic under easy interface, which I called "Vulkan AfterCrash". All you need to use it is just this single file: VulkanAfterCrash.h.
Update 4 April 2018: In GDC 2018 talk "Aftermath: Advances in GPU Crash Debugging (Presented by NVIDIA)", Alex Dunn announced that a Vulkan extension from NVIDIA will also be available, called VK_NV_device_diagnostic_checkpoints, but I can see it's not publicly accessible yet.
Update 1 August 2018: Documentation for extension VK_NV_device_diagnostic_checkpoints has been published in Vulkan version 1.1.82.
Update 12 September 2018: I've created similar, portable library for Direct3D 12 - see blog post "Debugging D3D12 driver crash".
# Vulkan Memory Allocator 2.0.0
At Game Developers Conference (GDC) last week I released final version 2.0.0 of Vulkan Memory Allocator library. It is now well documented and thanks to contributions from open source community it compiles and works on Windows, Linux, Android, and MacOS. Together with it I released VMA Dump Vis - a Python script that visualizes Vulkan memory on a picture. From now on I will continue incremental development on "development" branch and occasionally merge to "master". Feel free to contact me if you have any feedback, suggestions or if you find a bug.
# Memory management in Vulkan and DX12 - my talk at GDC 2018
If you happen to come to this year's Game Developers Conference (GDC), I'd like to invite you to my talk: "Memory management in Vulkan and DX12". During this lecture I will not only advertise my Vulkan Memory Allocator library, but I will also show technical details, tips and tricks for GPU memory management that you can use on your own when programming using Vulkan or Direct3D 12.
# VK_KHR_dedicated_allocation unofficial manual
I wrote a short article that explains how to use Vulkan extenion "VK_KHR_dedicated_allocation". It may be interesting to you if you are a programmer and you code graphics using Vulkan.
Go to article: VK_KHR_dedicated_allocation unofficial manual
# Vulkan Memory Allocator 2.0.0-alpha.3
I just published new version of Vulkan Memory Allocator 2.0.0-alpha.3. I'm quite happy with the quality of this code. Documentation is also updated, so if nothing else, please just go see User guide. I still marked it as "alpha" because I would like to ask for feedback and I may still change everything.
I would like to discuss proposed terminology. Naming things in code is a hard problem in general, and especially as English is not my native language, so please fill free to contact me and propose more elegant names to what I called: allocator, allocation, pool, block, stats, free range, used/unused bytes, own memory, persistently mapped memory, pointer to mapped data, lost allocation (becoming lost, making other lost), defragmentation, and used internally: suballocation, block vector.
# How to Use Vulkan SDK with AppVeyor and Travis CI?
AppVeyor and Travis CI are popular, free web services that provide continuous integration style build and testing environments for open source projects - for Windows and Linux, respectively. They are relatively easy to setup if your project is self-contained, but can be a little bit tricky if you need to install some additional dependencies. Today I successfully finished installing Vulkan SDK in these environments, to test Vulkan Memory Allocator project. Here is how to do it:
In AppVeyor I have everything configured on their website, so you can’t really see configuration file. To download Vulkan SDK, I used
curl --silent --show-error --output VulkanSDK.exe https://vulkan.lunarg.com/sdk/download/22.214.171.124/windows/VulkanSDK-126.96.36.199-Installer.exe
First command downloads and second one installs Vulkan SDK in silent mode. The SDK is installed to C:\VulkanSDK\188.8.131.52 directory.
Next I added an environmental variable in Environment > Environmental variables section:
In my Visual Studio project settings, I added include directory "$(VULKAN_SDK)/Include" and library directory "$(VULKAN_SDK)/Lib". Then I could successfully
#include <vulkan/vulkan.h> and link with vulkan-1.lib.
For Travis CI you can see my current configuration file as: .travis.yml. What I did here is I added few commands to
install section. First there are some
apt-get commands that install some additional libraries, which I took from Getting Started with the Vulkan SDK page:
sudo apt-get -qq update
sudo apt-get install -y libassimp-dev libglm-dev graphviz libxcb-dri3-0 libxcb-present0 libpciaccess0 cmake libpng-dev libxcb-dri3-dev libx11-dev libx11-xcb-dev libmirclient-dev libwayland-dev libxrandr-dev
Then I download and install Vulkan SDK. URL to real file is in the same format as for Windows. I used
wget command for downloading. The file is a self-extracting archive that unpacks SDK content to following subdirectory of current directory: VulkanSDK/184.108.40.206/x86_64.
wget -O vulkansdk-linux-x86_64-220.127.116.11.run https://vulkan.lunarg.com/sdk/download/18.104.22.168/linux/vulkansdk-linux-x86_64-22.214.171.124.run
chmod ugo+x vulkansdk-linux-x86_64-126.96.36.199.run
Finally I issue a command that sets environmental variable pointing to the SDK, to have it available in the code just like on Windows:
Then I needed to configure my project to search for include files in "$(VULKAN_SDK)/include" and library files in "$(VULKAN_SDK)/lib" (directory names are lowercase this time!). Finally I could
#include <vulkan/vulkan.h> and link with libvulkan.so.
# Understanding Vulkan objects
An important part of learning the Vulkan® API – just like any other API – is to understand what types of objects are defined in it, what they represent and how they relate to each other. To help with this, we’ve created a diagram that shows all of the Vulkan objects and some of their relationships, especially the order in which you create one from another.
Read more: Understanding Vulkan objects @ GPUOpen