Ubuntu – 18.04 mouse lag / IRQ disabled

I just installed Ubuntu Studio 18.04.1 (xfce4 desktop) and I experience a massive cursor lag of my USB mouse. Directly after login everything is fine mostly, but after [a random time] the mouse starts lagging. In the end I want to compile a rt-preempt kernel since this is supposed to be a DJ workstation, so it would be awesome to solve this before I dig into compiling a rt kernel…

I have the same issue when I boot the Ubuntu Studio 18.04.1 Live session from USB (also running 4.15.0-20-lowlatency #21-Ubuntu SMP PREEMPT).

Issueing dmesg | tail -100 after the lag appears always gives me

irq 18: nobody cared (try booting with the "irqpoll" option)
CPU: 2 PID: 111 Comm: irq/18-ohci_hcd Tainted: G          I      4.15.0-20-lowlatency #21-Ubuntu
Hardware name: LENOVO 12003NG/12003NG, BIOS GBET02WW(1.02) 12/06/2011
Call Trace:
 <IRQ>
 dump_stack+0x63/0x8b
 __report_bad_irq+0x35/0xc0
 note_interrupt+0x24b/0x2a0
 handle_irq_event_percpu+0x54/0x80
 handle_irq_event+0x39/0x60
 handle_fasteoi_irq+0x75/0x130
 handle_irq+0x20/0x30
 do_IRQ+0x46/0xd0
 common_interrupt+0x84/0x84
 </IRQ>
RIP: 0010:ohci_irq+0x2f/0x2c0
RSP: 0018:ffffc000c11dbe40 EFLAGS: 00000213 ORIG_RAX: ffffffffffffffd9
RAX: ffffffffba560630 RBX: ffff9988d55f4000 RCX: 0000000000000002
RDX: 0000000000000024 RSI: ffff9988d55f4000 RDI: ffff9988d55f4000
RBP: ffffc000c11dbe68 R08: ffff9988ded03f08 R09: 0000000000000101
R10: 000000000007a120 R11: ffffc000c11dbe50 R12: ffffc000c0ce1000
R13: 000000008000005a R14: ffff9988cb65b2a4 R15: ffff9988cb6fca00
 ? ohci_bus_resume+0x90/0x90
 ? irq_finalize_oneshot.part.40+0xe0/0xe0
 usb_hcd_irq+0x2c/0x40
 irq_forced_thread_fn+0x2f/0x70
 ? irq_finalize_oneshot.part.40+0xe0/0xe0
 irq_thread+0x145/0x1a0
 ? wake_threads_waitq+0x30/0x30
 kthread+0x121/0x140
 ? irq_thread_dtor+0xa0/0xa0
 ? kthread_create_worker_on_cpu+0x70/0x70
 ret_from_fork+0x22/0x40
handlers:
[<00000000e94e8f9e>] irq_default_primary_handler threaded [<00000000d156bb10>] usb_hcd_irq
[<00000000e94e8f9e>] irq_default_primary_handler threaded [<00000000d156bb10>] usb_hcd_irq
[<00000000e94e8f9e>] irq_default_primary_handler threaded [<00000000d156bb10>] usb_hcd_irq
[<00000000e94e8f9e>] irq_default_primary_handler threaded [<00000000933e1421>] _rtl_pci_interrupt [rtl_pci]
Disabling IRQ #18

cat /proc/interrupts tells me IRQ 18 is shared by those devices:
ohci_hcd:usb4, ohci_hcd:usb5, ohci_hcd:usb6, rtl_pci (network I guess)

I'm clueless how to get rid of that lag.
What I tried so far (and didn't help):

• choose another session at the login screen (Ubuntu Studio OR xfce session)
• boot with irqpoll
• drm_kms_helper approach from i.e. here
• unplug & re-plug the mouse
• use another USB port
• use another USB mouse (Logitech wireless)

Other facts:

• mouse (and machine in general) is running perfectly fine with Ubuntu Studio 14.04.5 with 4.4 standard kernel and 3.18 rt-preempt kernel
• no extra power manager installed like it seems to be the issue here
• can't properly test with standard kernel since I won't get a few things working with it