linux-kernel - Re: Bug report for kernel v4.15-rc8+

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Message-ID: <87tujwhxl2.ffs@tglx>
Date:   Wed, 11 Aug 2021 16:20:41 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     blinkin@...il.it
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org
Subject: Re: Bug report for kernel v4.15-rc8+

On Wed, Aug 11 2021 at 15:51, blinkin@...il.it wrote:
> 1) You're booting with an out of tree module
>
>   Uninstalled virtualbox, reproduced same behavior without the module.
>   dmesg outputs attached with and without the workaround
>   (dmesg_novboxdrv_clean.txt and dmesg_novboxdrv_irqaffinity0.txt)

Ok.

> 2) Please provide information what is consuming 90% of a CPU
>
>   top shows a kworker process consistently at 50% without the
>   workaround, 60% with the workaround. No significant activity amounts
>   from other processes.  Sometimes that 50% is split between two
>   kworker processes for a short time.  CPU core #0 activity is a
>   constant 60% without the workaround, 90% with the workaround

That's broken. /proc/interrupts gives some hint:

1) Stock kernel

>             CPU0       CPU1       CPU2       CPU3       
>    0:         10          0          0          0  IR-IO-APIC    2-edge      timer
>    1:          0          0          0          9  IR-IO-APIC    1-edge      i8042
>    8:          0          1          0          0  IR-IO-APIC    8-edge      rtc0
>    9:          0     923411          0          0  IR-IO-APIC    9-fasteoi   acpi

900k ACPI interrupts right after boot

>             CPU0       CPU1       CPU2       CPU3       
>    0:         10          0          0          0  IR-IO-APIC    2-edge      timer
>    1:          0          0          0         11  IR-IO-APIC    1-edge      i8042
>    8:          0          1          0          0  IR-IO-APIC    8-edge      rtc0
>    9:          0    4869059          0          0  IR-IO-APIC    9-fasteoi   acpi

One minute later it's 4.8M

With affinity forced to CPU0 it's even more:

>             CPU0       CPU1       CPU2       CPU3       
>    0:         10          0          0          0  IR-IO-APIC    2-edge      timer
>    1:          9          0          0          0  IR-IO-APIC    1-edge      i8042
>    8:          1          0          0          0  IR-IO-APIC    8-edge      rtc0
>    9:    7576456          0          0          0  IR-IO-APIC    9-fasteoi   acpi

7.5M right after boot

>             CPU0       CPU1       CPU2       CPU3       
>    0:         10          0          0          0  IR-IO-APIC    2-edge      timer
>    1:         11          0          0          0  IR-IO-APIC    1-edge      i8042
>    8:          1          0          0          0  IR-IO-APIC    8-edge      rtc0
>    9:   10992420          0          0          0  IR-IO-APIC    9-fasteoi   acpi

10.9M after one minute. Though the delta between right after boot and 1
minute later is in the same ballpark.

Cc'ed the ACPI people for clues.

Thanks,

        tglx