Debugging operating systems with time-traveling virtual machines
Cyclic debugging
Problems with cyclic debugging
Example: NULL pointer
Example: NULL pointer
Debugging with time traveling virtual machines
Overview
Debugging with time traveling virtual machines (TTVM)
Time-Traveling virtual machine
Typical OS level debugging
Using virtual-machines for debugging
Checkpoints
ReVirt
How to time travel backward
Using time travel to implement reverse watchpoints
Performance
Performance
Experiences with TTVM
Experiences with TTVM
Conclusions
Reference

ReVirt

Based on previous work Re-executes any part of the prior run, instruction by instruction Re-creates all state at any prior point in the run Logs all sources of non-determinism external input (keyboard, mouse, network card, clock) interrupt point Low space and time overhead SPECweb, PostMark, kernel compilation logging adds 3-12% time overhead logging adds 2-85 KB/sec