IRQs in /proc/irq/* that aren't listed in /proc/interrupts?

IRQs in /proc/irq/* that aren't listed in /proc/interrupts?

[Chris Friesen]

Hi,

On one of my X86-64 systems /proc/interrupts starts with the following 
interrupts (per-cpu info snipped):

   0:      IR-IO-APIC-edge      timer
    4:      IR-IO-APIC-edge      serial
    8:      IR-IO-APIC-edge      rtc0
    9:      IR-IO-APIC-fasteoi   acpi
   17:      IR-IO-APIC-fasteoi   ehci_hcd:usb1, hpilo


On this same system /proc/irq shows these interrupts:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
17

Is there any way to determine what the interrupts are that aren't listed 
in /proc/interrupts?  Six of them are affined to all CPUs, and I'm 
trying to affine as many interrupts as possible to housekeeping CPUs to 
free up application CPUs for low-latency operations.

I'm not subscribed to the list, so I'd appreciate being CC's on any replies.

Chris

Re: IRQs in /proc/irq/* that aren't listed in /proc/interrupts?

[Thomas Gleixner]

Chris,

On Mon, Oct 12 2020 at 12:40, Chris Friesen wrote:
> On one of my X86-64 systems /proc/interrupts starts with the following 
> interrupts (per-cpu info snipped):
>
>    0:      IR-IO-APIC-edge      timer
>     4:      IR-IO-APIC-edge      serial
>     8:      IR-IO-APIC-edge      rtc0
>     9:      IR-IO-APIC-fasteoi   acpi
>    17:      IR-IO-APIC-fasteoi   ehci_hcd:usb1, hpilo
>
>
> On this same system /proc/irq shows these interrupts:
>
> 0-15, 17
>
> Is there any way to determine what the interrupts are that aren't listed 
> in /proc/interrupts?

They are simply unused.

> Six of them are affined to all CPUs, and I'm trying to affine as many
> interrupts as possible to housekeeping CPUs to free up application
> CPUs for low-latency operations.

Affining unused and therefore disabled interrupts is a pretty pointless
exercise.

Thanks,

        tglx

Re: IRQs in /proc/irq/* that aren't listed in /proc/interrupts?

[Chris Friesen]

On 10/12/2020 1:37 PM, Thomas Gleixner wrote:
> On Mon, Oct 12 2020 at 12:40, Chris Friesen wrote:
>> On one of my X86-64 systems /proc/interrupts starts with the following
>> interrupts (per-cpu info snipped):
>>
>>     0:      IR-IO-APIC-edge      timer
>>      4:      IR-IO-APIC-edge      serial
>>      8:      IR-IO-APIC-edge      rtc0
>>      9:      IR-IO-APIC-fasteoi   acpi
>>     17:      IR-IO-APIC-fasteoi   ehci_hcd:usb1, hpilo
>>
>>
>> On this same system /proc/irq shows these interrupts:
>>
>> 0-15, 17
>>
>> Is there any way to determine what the interrupts are that aren't listed
>> in /proc/interrupts?
> 
> They are simply unused

I wonder if it might be clearer to just not report them at all if 
they're not used?

Anyways, thanks for the explanation.

Chris