Kernel: LWN Linux Articles (Now Free), Testers Wanted
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CPU frequency governors and remote callbacks
The kernel's CPU-frequency ("cpufreq") governors are charged with picking an operating frequency for each processor that minimizes power use while maintaining an adequate level of performance as determined by the current policy. These governors normally run locally, with each CPU handling its own frequency management. The 4.14 kernel release, though, will enable the CPU-frequency governors to control the frequency of any CPU in the system if the architecture permits, a change that should improve the performance of the system overall.
For a long time, the cpufreq governors used the kernel's timer infrastructure to run at a regular interval and sample CPU utilization. That approach had its shortcomings; the biggest one was that the cpufreq governors were running in a reactive mode, choosing the next frequency based on the load pattern in the previous sampling period. There is, of course, no guarantee that the same load pattern will continue after the frequency is changed. Additionally, there was no coordination between the cpufreq governors and the task scheduler. It would be far better if the cpufreq governors were proactive and, working with the scheduler, could choose a frequency that suits the load that the system is going to have in the next sampling period.
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A last-minute MMU notifier change
One does not normally expect to see significant changes to an important internal memory-management mechanism in the time between the ‑rc7 prepatch and the final release for a development cycle, but that is exactly what happened just before 4.13 was released. A regression involving the memory-management unit (MMU) notifier mechanism briefly threatened to delay this release, but a last-minute scramble kept 4.13 on schedule and also resulted in a cleanup of that mechanism. This seems like a good time to look at a mechanism that Linus Torvalds called "a badly designed mistake" and how it was made to be a bit less mistaken.
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A pile of stable kernel updates
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Improving Linux laptop battery life: Testers Wanted
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