2.14. Reduce CPU Performance Spikes

The kernel command line parameter skew_tick helps to smooth jitter on moderate to large systems with latency-sensitive applications running. A common source of latency spikes on a realtime Linux system is when multiple CPUs contend on common locks in the Linux kernel timer tick handler. The usual locks responsible for the contention are the xtime_lock, which is used by the timekeeping system, and the RCU (Read-Copy-Update) structure locks.

Using the skew_tick=1 boot parameter reduces contention on these kernel locks. The parameter ensures that the ticks per CPU do not occur simultaneously by making their start times 'skewed'. Skewing the start times of the per-CPU timer ticks decreases the potential for lock conflicts, reducing system jitter for interrupt response times.