Rescheduling Interrupt

[H C <hc128168@xxxxxxxxx>]

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

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