Bisected: The Unfortunate Reason Linux 4.20 Is Running Slower (opens in new tab)

(phoronix.com)

18 pointsrsendv7y ago4 comments

4 comments

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.

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.

j / k navigate · click thread line to collapse

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.

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.

j / k navigate · click thread line to collapse