What is Windows *doing* while hogging that lock

Random ASCII - tech blog of Bruce Dawson

Earlier this month I wrote about how Windows 10 holds a lock during too much of process destruction, which both serializes this task and causes mouse-cursor hitches and UI hangs (because the same lock is used for these UI tasks).

I thought I’d use this as an excuse to dig slightly deeper into what is going on using a clunky-but-effective ETW profiling technique. This technique shows that a 48 instruction loop is consuming a huge chunk of the CPU time while the lock is held – the 80/20 rule is alive and well. And, thanks to some discussion on hacker news I know have an idea of what that function does and why it got so much more expensive in Windows 10 Anniversary Edition.

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