tickless kernel
also: CONFIG_NO_HZ, tickless mode, dynamic ticks, no-Hz kernel
A kernel that doesn't rely on periodic timer interrupts (clock ticks) to manage scheduling and time-keeping. Instead, it uses event-driven timers that only fire when needed, reducing CPU wake-ups and power consumption.
Traditional Linux kernels use a timer interrupt that fires at fixed intervals (typically 100-1000 Hz), forcing the CPU to wake up even when idle to check for work. A tickless kernel eliminates these unnecessary interrupts by using dynamic timers that only trigger when an actual event (like a process becoming runnable) occurs.
This is particularly beneficial for power management and latency-sensitive systems. On laptops and mobile devices, fewer interrupts mean the CPU can stay in low-power states longer. On real-time systems, it reduces jitter from constant timer overhead.
Tickless kernels are enabled via the CONFIG_NO_HZ kernel option. Modern Linux kernels use CONFIG_NO_HZ_FULL for isolated CPUs that can run completely without ticks, crucial for high-performance computing and latency-critical applications.