Bisected: The Unfortunate Reason Linux 4.20 Is Running Slower
phoronix.comtl;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.
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.
It gets websites more clicks.
A 30% performance drop is pretty shocking.