Timeout Detection and Recovery of GPUs through WDDM
Updated: April 27, 2009
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One of the most common stability problems in graphics is when the system appears completely "frozen" or "hung" while processing an end-user command or operation. Users generally wait a few seconds and then reboot the system by pressing the Power button. Usually the graphics processing unit (GPU) is "busy" processing intensive graphical operations, typically during gameplay. This results in nothing being updated on the screen, thus appearing to the user that the system is frozen.
This paper briefly describes the timeout detection and recovery (TDR) process in Windows Vista. It also documents the registry controls so developers can easily debug problems.
What's New for Windows Vista SP1
Timeout Detection and Recovery
Windows Vista attempts to detect these problematic hang situations and recover a responsive desktop dynamically. In this process, the Windows Display Driver Model (WDDM) driver is reinitialized and the GPU is reset. No reboot is necessary, which greatly enhances the user experience. The only visible artifact from the hang detection to the recovery is a screen flicker, which results from resetting some portions of the graphics stack, causing a screen redraw. Some older Microsoft DirectX applications may render to a black screen at the end of this recovery. The end user would have to restart these applications.
The following is a brief overview of the TDR process:
Windows Vista SP1 Update
Minor changes were made in Windows Vista SP1 to improve the user experience in cases of frequent and rapidly occurring GPU hangs. Repetitive GPU hangs indicate that the graphics hardware has not recovered successfully. In these instances, the system must be shut down and restarted to fully reset the graphics hardware. If the operating system detects that six or more GPU hangs and subsequent recoveries occur within 1 minute, then the following GPU hang is treated as a system bug check.
Throughout the process of GPU hang detection and recovery, the desktop is unresponsive and thus unavailable to the user. In the final stages of recovery, a brief screen flash occurs that is similar to the one when the screen resolution is changed. After the desktop has been successfully recovered, the following informational message appears to the user.
The message is also logged in the Windows Vista Event Viewer. Diagnosis information is collected in the form of a debug report that is returned to Microsoft through the Online Crash Analysis (OCA) mechanism if the user opts in to provide feedback.
The following registry keys are documented for testing purposes only. These registry keys should not be manipulated by any applications outside targeted testing or debugging.
The TDR-related registry keys are located under HKLM\System\CurrentControlSet\Control\GraphicsDrivers.
Graphics hardware vendors:
Graphics software vendors:
Queries: If you have questions that are not answered in this document, send e-mail to email@example.com.