Hi, My machine is running CentOS 7 with 3.10.0-1127.19.1.el7.x86_64, and I noticed that my application (it is a dummy C++ application with an infinite tight loop calling rand()) keeps getting rescheduling interrupts per /proc/interrupts and only nr_involuntary_switches is increasing (per /proc/<pid>/sched) by 2 every second. My kernel parameters: rcu_nocbs=2-17 isolcpus=2-17 rcu_nocb_poll irqaffinity=0 noapic nowatchdog Tho, bcc tool shows that someone is still calling apic_timer_interrupt() (although kernel parameter above says noapic): # taskset -c 6 /usr/share/bcc/tools/stackcount -p 2496 native_smp_send_reschedule Tracing 1 functions for "native_smp_send_reschedule"... Hit Ctrl-C to end. ^C native_smp_send_reschedule activate_task ttwu_do_activate try_to_wake_up wake_up_process wake_up_worker insert_work __queue_work delayed_work_timer_fn call_timer_fn run_timer_softirq __do_softirq call_softirq do_softirq irq_exit smp_apic_timer_interrupt apic_timer_interrupt [unknown] [unknown] 1 native_smp_send_reschedule activate_task ttwu_do_activate try_to_wake_up wake_up_process wake_up_worker insert_work __queue_work delayed_work_timer_fn call_timer_fn run_timer_softirq __do_softirq call_softirq do_softirq irq_exit smp_apic_timer_interrupt apic_timer_interrupt [unknown] [unknown] 1 Any idea how to turn off this interrupt? I have another Skylake machine (different CPU from the tested one above but same architecture -- Skylake), and it has no such issue at all. Thanks! Cheers, Henry