[LAU] kernel 5.15 irqs

[David Kastrup]

Len Ovens <len at ovenwerks.net> writes:

> In older kernels running:
>  pa ax |grep irq
> will show a process for each irq in the form:
>     548 ?        S      0:00 [irq/16-snd_ens1]
>
> however, with kernel 5.15 most of these are gone except the one for
> mei_me. This means that rtirq doesn't work and my device suffers from
> more xruns than normal.
>
> Has anyone else experienced this?

Are you running your kernel with the threadirqs option?

$ cat /proc/version
Linux version 5.15.0-18-lowlatency (buildd at lcy02-amd64-041) (gcc (Ubuntu 11.2.0-14ubuntu1) 11.2.0, GNU ld (GNU Binutils for Ubuntu) 2.37.50.20220106) #18-Ubuntu SMP PREEMPT Fri Jan 21 15:51:07 UTC 2022

$ cat /proc/cmdline 
BOOT_IMAGE=/vmlinuz-5.15.0-18-lowlatency root=UUID=XXX ro threadirqs quiet splash threadirqs resume=UUID=XXX vt.handoff=1

$ ps ax|grep irq
     12 ?        S      0:18 [ksoftirqd/0]
     21 ?        S      0:13 [ksoftirqd/1]
     27 ?        S      0:15 [ksoftirqd/2]
     33 ?        S      0:22 [ksoftirqd/3]
     39 ?        S      0:22 [ksoftirqd/4]
     45 ?        S      0:12 [ksoftirqd/5]
     51 ?        S      0:16 [ksoftirqd/6]
     57 ?        S      0:15 [ksoftirqd/7]
    120 ?        S      0:00 [irq/9-acpi]
    142 ?        I<     0:00 [vfio-irqfd-clea]
    143 ?        S      0:00 [irq/16-ehci_hcd]
    144 ?        S      3:44 [irq/23-ehci_hcd]
    145 ?        S      2:33 [irq/12-i8042]
    146 ?        S      0:04 [irq/1-i8042]
    147 ?        S      0:00 [irq/8-rtc0]
    230 ?        S      0:00 [irq/18-i801_smb]
    234 ?        S      0:00 [irq/16-mmc0]
    235 ?        S      0:00 [irq/16-s-mmc0]
    239 ?        S      0:00 [irq/19-firewire]
    242 ?        S      0:04 [irq/25-ahci[000]
    281 ?        S      0:31 [irq/26-i915]
    500 ?        S      0:00 [irq/27-mei_me]
    548 ?        S      0:24 [irq/28-iwlwifi]
    549 ?        S      0:36 [irq/28-s-iwlwif]
    598 ?        S      0:00 [irq/29-snd_hda_]
   1082 ?        Ssl    0:01 /usr/sbin/irqbalance --foreground
   1664 ?        S      0:08 [irq/24-enp0s25]
  18689 pts/1    S+     0:00 grep --color=auto irq


-- 
David Kastrup