Background

Currently, wgpu keeps around a pool of staging buffers that are DEVICE_LOCAL_BIT | HOST_VISIBLE_BIT | HOST_COHERENT_BIT. Writes to GPU buffers are first written here, and then copied to the final GPU buffers. This is because systems are sometimes limited by the 256MB PCI-E limit, meaning the only DEVICE_LOCAL_BIT | HOST_VISIBLE_BIT | HOST_COHERENT_BIT heap you had was 256 MB.

However, for mobile GPUs, integrated GPUs, and now desktops with resizable bar, this limitation is removed. These devices have heaps with DEVICE_LOCAL_BIT | HOST_VISIBLE_BIT | HOST_COHERENT_BIT that range into the GBs. There's no need for staging buffers in this case.

Feature Request

wgpu should check the size of the DEVICE_LOCAL_BIT | HOST_VISIBLE_BIT | HOST_COHERENT_BIT it uses for buffer writes, and if it's greater than 256 MB, skip creating staging buffers. wgpu will then just directly write to buffers.