Full DynTicks Proposed For Linux Kernel Integration

Aside from the KVM pull request, another interesting proposed change for the Linux 3.10 kernel is the "full dynticks" support, also known as CONFIG_NO_HZ_FULL. Ingo Molnar is trying to get this brand new feature into the next Linux kernel release.

Ingo Molnar wrote a lengthy request to Torvalds to pull the Git feature branch that provides full dynticks / CONFIG_NO_HZ_FULL. This is the work largely done by Frederic Weisbecker as part of an adaptive tickless kernel and can yield performance improvements.

The "full dynticks" option is a core kernel feature and extends the earlier dynamic ticks feature to work on busy CPUs too rather than just those idling. This can yield a reduction in the number of timer interrupts that are generated by quite a lot.

This CONFIG_NO_HZ_FULL support is of interest in particular to real-time Linux users and also can be of great benefit to HPC (High Performance Computing) workloads where there is only one task running (performance improvements by maybe 1%), a reduction in real-time workload latency, and can also help desktop and mobile users where there is just one CPU task active on a given core. The only downside to this work is longer to-idle and from-idle latency.

Kernel developers are hoping to have this feature introduced into the Linux 3.10 kernel but there is still a bit uncertainty as there are some loose ends remaining and other small changes the developers are still looking at doing in the near future. Regardless, it should be an interesting kernel feature to benchmark once it's been merged to mainline.