How to get VRAM usage via C++

Development Programming & Scripting C++
2

Surprised it took 5 years for someone to figure this out, but here’s how you do it. This will allow you to retrieve used, available, and total VRAM figures, but only on Windows.

  1. Create a new gameplay module. You can follow the guide in the Unreal Docs here.
  2. The new module should have the following *.Build.cs file contents:
using UnrealBuildTool;

public class LowLevelTelemetry : ModuleRules {
  public LowLevelTelemetry(ReadOnlyTargetRules Target) : base(Target) {
    PrivateDependencyModuleNames.AddRange(new string[] {
      "Core",
      "CoreUObject",
      "Engine"
    });

    PublicIncludePathModuleNames.AddRange(new string[] { "RHI" });

    if ((Target.IsInPlatformGroup(UnrealPlatformGroup.Windows)))
    {
      // Uses DXGI to query GPU hardware
      // This is what will allow us to get GPU usage statistics at runtime
      PublicSystemLibraries.Add("DXGI.lib");
    }
  }
}
  1. In the module’s main header file, add the following includes:
#include <CoreMinimal.h>
#include "Windows/WindowsHWrapper.h"

THIRD_PARTY_INCLUDES_START
#include "Windows/AllowWindowsPlatformTypes.h"
#include "Windows/PreWindowsApi.h"
#include "dxgi1_4.h"
#include "Windows/PostWindowsApi.h"
#include "Windows/HideWindowsPlatformTypes.h"
THIRD_PARTY_INCLUDES_END
  1. Now for the implementations:
static size_t GetUsedVideoMemory() {
    IDXGIFactory4* pFactory;
    CreateDXGIFactory1(__uuidof(IDXGIFactory4), (void**)&pFactory);

    IDXGIAdapter3* adapter;
    pFactory->EnumAdapters(0, reinterpret_cast<IDXGIAdapter**>(&adapter));

    DXGI_QUERY_VIDEO_MEMORY_INFO videoMemoryInfo;
    adapter->QueryVideoMemoryInfo(0, DXGI_MEMORY_SEGMENT_GROUP_LOCAL, &videoMemoryInfo);

    size_t usedVRAM = videoMemoryInfo.CurrentUsage / 1024 / 1024;

    return usedVRAM;
}

You can get

videoMemoryInfo.AvailableForReservation

and

videoMemoryInfo.Budget

to get available and total VRAM as well.

  1. Add the new module as a dependency to your game module (YourGame.Build.cs):
PrivateDependencyModuleNames.AddRange(new string[] {
    "YourNewModule"
});

That’s it, tested and working in 5.1. Hope that helps!

References:

6 Likes