September 5, 2018

Linux Weather Forecast

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Linux weather forecast
Linux "chief meteorologist" Jonathan Corbet shares the current conditions for Linux kernel development.

Welcome to the Linux Weather Forecast

This page is an attempt to track ongoing developments in the Linux development community that have a good chance of appearing in a mainline kernel and/or major distributions sometime in the near future. Your "chief meteorologist" is Jonathan Corbet, Executive Editor at LWN.net. If you have suggestions on improving the forecast (and particularly if you have a project or patchset that you think should be tracked), please add your comments below.

Forecast Summaries

Current conditions: the 4.18 kernel was released on August 12. Some of the more important changes in this release are:

  • The power domains subsystem has seen a number of enhancements that will lead to improved whole-system power management.
  • It is now possible for unprivileged processes to mount filesystems when running in a user namespace. This will make it possible to mount filesystems within containers without the need for additional privileges.
  • Zero-copy TCP data reception is now supported.
  • The AF_XDP subsystem will eventually lead to highly accelerated networking in a number of settings. This work is part of a larger effort to win back users of user-space networking stacks by providing better facilities in the kernel.
  • Bpfilter is a new packet-filtering mechanism based on the BPF virtual machine. The 4.18 version of bpfilter won't do much, but it is expected to be the base on which the next generation of kernel firewalling systems is built.
  • Restartable sequences, a new API for performing highly optimized lockless operations in user space, have finally made it into the mainline kernel.

It's also worth noting that the new AIO-based polling mechanism, originally merged for 4.18, was later reverted pending further work.

The 4.18 development cycle saw the merging of 13,283 unique changesets from nearly 1,700 developers, 226 of whom where first-time contributors. See this article for more information on the changes merged for 4.18.

Short-term forecast: The 4.19 kernel can be expected in mid-October. Some of the key features merged for this release are:

  • The AIO-based polling mechanism that didn't quite make 4.18 will be there in 4.19.
  • Load tracking in the scheduler has been augmented with a better understanding of the resources used by realtime and deadline processes; this information will support better power-management decisions.
  • Intel's cache pseudo-locking feature is now supported.
  • An extensive set of mitigations for the L1TF vulnerability has been provided.
  • The block I/O latency controller allows an administrator to provide block (disk) I/O response-time guarantees to specific processes.
  • Time-based packet transmission is now supported in the networking subsystem.
  • The CAKE queueing discipline offers significantly better networking performance, especially in home or small-business settings.
  • The minimum version of GCC needed to build the kernel is now 4.6.
  • As usual, thousands of bug fixes, clean-ups, and small improvements have been merged as well.

The 4.19 kernel is in the stabilization phase now, with only bug fixes accepted. There is a small chance that this kernel will be called "5.0" when it is released, though your weatherman would predict that 5.0 won't happen for one more release cycle.

This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 License.

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