Download fresh Vivaldi Stable - 3.6 (2165.34). Open non existent domain to land on a very light "this page doesnt exist" ERR_NAME_NOT_RESOLVED error page. Start Cloning Tabs by Shift clicking in the Tab bar, then Right clicking and selecting Clone. First you clone one tab into two, then two into four, etc. At cloning 64 Tabs to 128 opening every new Tab will be taking ~1 second per Tab. Cloning up to 256 open tabs will take you anywhere between 5-15 minutes!!! At this point switching between Tabs will FREEZE UI for 8 seconds.
Let me repeat - EIGHT second freeze while switching between empty error page Tabs.
At all times Vivaldi UI will be freezing with one maxed out thread of 16 thread 4GHz CPU, other 15 threads resting at minimal load.
Right clicking on the first open tab and selecting "close Tabs to the Right" will close 255 Tabs at once - this will FREEZE UI for ~1.5 minutes. >100 seconds of frozen UI while browser is closing 255 empty html only Tabs. Again one CPU thread maxed out, rest idle.
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