Linux kernel 2.6.24 with new Wi-Fi drivers
Summary
In January 2008 Linux 2.6.24 brought additional Wi-Fi drivers for the new Wi-Fi subsystem and the power-saving tickless feature for further architectures besides x86. The Completely Fair Scheduler introduced with 2.6.23 was optimised and learned fair group scheduling. This allowed priorities to be assigned to users or process groups, for example to favour multimedia or compilers.
Ideas
- Tickless operation saves power because the CPU is not woken at a fixed rate.
- CFS calculates in nanoseconds instead of jiffies.
- Group scheduling distributes CPU time fairly between users rather than only between processes.
- USB authorisation laid the foundation for Wireless USB.
Insights
- Fairness between groups prevents one user with many processes from crowding out everyone else.
- From the mid-2000s, saving power became a central kernel topic.
Facts
- The Completely Fair Scheduler arrived with Linux 2.6.23.
- CFS could switch between desktop and server optimisation during operation.
- New in the kernel were, among others, the Wi-Fi drivers iwlwifi, rt2x00 and b43.
References
Critique
- The report describes features without measurements of power consumption or response times.
Remarks
- Group scheduling developed into cgroups, which systemd and containers use today; CFS was replaced by EEVDF in 2023.
Recommendations
- Limit services’ CPU shares via systemd slices and cgroups.
- Use powertop to check whether services cause unnecessary wakeups.
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