[craftyguy]

tl;dr: The cause is the Single Thread Indirect Branch Predictors (STIBP) for cross-hyperthread Spectre mitigation on Intel processors.

I'm not sure why Michael thinks this is a surprise, performance regressions were practically on the box with these mitigations.

[liamkinne]

I don't get the general shock that people have over these mitigations slowing performance.

Yeah we're throwing out the cash more often, of course it's going to be slower.

[craftyguy]

It gets websites more clicks.

[FartyMcFarter]

A 30% performance drop is pretty shocking.