In rare cases, calling ID3D11DeviceContext::Flush may stall internally for a few hundred ms. if you check the call stack with PIX or something, it looks like it is waiting for something inside nvwgf2umx as follows.
FFFFFFF80454009FB8 ntoskrnl!
00007FFBDB02CFC4 ntdll!ZwWaitForSingleObject+0x14
00007FFBD8941ACE KernelBase!WaitForSingleObjectEx+0x8E
00007FFB9082692F nvwgf2umx!
00007FFB908277F0 nvwgf2umx!
00007FFB90827E39 nvwgf2umx!
00007FFB908A1BFC nvwgf2umx!
00007FFBD3A6AE97 d3d11!NDXGI::CDevice::Flush+0xA7
00007FFBD3A6ADA6 d3d11!NDXGI::CDevice::FlushAndEnqueueSetEvent+0x5E
00007FFBD3B4EA57 d3d11!CContext::TID3D11DeviceContext_Flush_AppEntered+0x87
Does anyone have any information or investigative techniques that could cause this?
development environment
OS – Windows 10 pro
GPU – NVIDIA GeForce 2070 super
CPU – AMD Ryzen 7 3700X 8-Core Processor 3.59 GHz
RAM – 64GB