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Linux 6.15 Shipped With A Nasty Power Regression For Some Systems


The Linux 6.15 kernel that shipped as stable last week mistakenly shipped with a nasty CPU power regression for some systems

"Revert commit 96040f7273e2 ("x86/smp: Eliminate mwait_play_dead_cpuid_hint()") because it introduced a significant power regression on systems that start with "nosmt" in the kernel command line. Later on, when the processor attempts to enter a deep package C-state, including PC10 which is requisite for reaching minimum power in suspend-to-idle, it is not able to do that because of the SMT siblings staying in C1 (which they have been put into by HLT). That original patch intended to address an issue affecting at least Intel Xeon 6 "Sierra Forest" C-states.

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