The 3.10 Merge Window Closes

Linus Torvalds made a Mother’s Day gift to the world in the form of the 3.10-rc1 kernel prepatch. With this release, the merge window for the 3.10 development cycle has closed, so we know which features to expect this time around.

The feature that has arguably drawn the most attention is one that will probably not have a huge effect for most users: the addition of (nearly) full dynamic tick support. The periodic “timer tick” is an interrupt that is delivered every 1-10ms while the CPU is busy; it is the kernel’s cue to perform various important housekeeping tasks. It is also a distraction from the work the user really wants done and it can slow down the system’s response time slightly. That slowdown is especially irksome to some high-performance computing and realtime users.

In 3.10, the kernel can turn off the timer tick in some situations, but most users will notice no performance difference. The suppression of the timer tick should happen more widely in future kernel releases; meanwhile it is an interesting bit of work and a significant step forward for the core kernel. Congratulations are due to Frederic Weisbecker, who did the bulk of the heavy lifting in this effort.

Other significant changes include a number of tracing improvements, a mechanism by which user space can be notified when the system is under memory pressure, and the bcache storage caching layer. See the Linux Weather Forecast page for a more complete list.

In the end, nearly 12,000 independent changes were pulled into the mainline during the twelve-day merge window. That makes this merge window the busiest in kernel development history and suggests that the final 3.10 release (due in early July) will be the largest kernel development cycle ever. The kernel and the community that develops it continue to grow.