Looks like severe degradation in immersive shell start time in Insider Dev. This synchronous single-thread shitfest makes startup / login 10+ seconds slower for me. Among fresh contributors are virtual desktops and feeds (news & interests).
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Aha. It turns out virtual desktop initialization is asking for desktop wallpaper change, but desktop thread is busy arranging invisible icons in quadratic time:
And yes, this bullshit was cherry-picked to 1909/2004/20H2/21H1/whatever 'stable' win10.
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