Bisected: The Unfortunate Reason Linux 4.20 Is Running Slower

Post by craftyguy » Fri, Nov 16, 2018, 11:49 PM UTC

Post by craftyguy » Sat, Nov 17, 2018, 1:13 AM UTC

liamkinne wrote: post #3

craftyguy wrote: post #2

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.

Post by FartyMcFarter » Sat, Nov 17, 2018, 11:05 PM UTC

liamkinne wrote: post #3

craftyguy wrote: post #2

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.