Major slowdowns caused by the new Linux 4.20 kernel have been traced to a mitigation for Spectre variant 2 that Linux founder Linus Torvalds now wants restricted.
As noted by Linux news site Phoronix, the sudden slowdowns have been caused by a newly implemented mitigation called Single Thread Indirect Branch Predictors (STIBP), which is on by default in the Linux 4.20 kernel for Intel systems with up-to-date microcode.
STIBP is one of three possible mitigations Intel added to its firmware updates in response to the Spectre v2 attacks. Others included Indirect Branch Restricted Speculation (IBRS), and Indirect Branch Predictor Barrier (IBPB), which could be enabled by operating-system makers.
Read more at ZDNet