Date:   Wed, 11 Aug 2021 15:51:10 +0200 (CEST)
From:   blinkin@...il.it
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Bug report for kernel v4.15-rc8+

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)

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

> 3) Please provide the output of /proc/interrupts for both boot scenarios

  attached:
  interrupts_clean.txt, interrupts_after1min_clean.txt (reproducing bug)
  interrupts_irqaffinity0.txt and interrupts_after1min_irqaffinity0.txt (with workaround)


P.S.: I don't know if it can help, but the behavior is worse in later kernel versions. I can't pinpoint a precise version because it looks like a gradual effect, but I can tell v4.19 and later versions are performing worse than 4.15-rc9. Actually in 4.15-rc9 the slowness is apparent only when doing resource-intensive tasks like playing 3d games, while for example in 4.19 I experience missed clicks and keyboard typing delay with just a text editor)

Thanks for the support

----- Messaggio originale -----
Da: "Thomas Gleixner" <tglx@...utronix.de>
A: blinkin@...il.it
Cc: "linux-kernel" <linux-kernel@...r.kernel.org>
Inviato: Martedì, 10 agosto 2021 19:09:32
Oggetto: Re: Bug report for kernel v4.15-rc8+

On Tue, Aug 10 2021 at 16:05, blinkin@...il.it wrote:
> The general symptom is a slow and unresponsive system (e.g. on gnome
> there's a delay before displaying typed characters, up to 3-5
> seconds. Animations are jittering, mouse clicks sometimes are missed).
> 3D games are now impossible to play due to poor performance.
>
> System feels as if the CPU is always busy (htop shows one core at ~
> 90% most of the time both with and without the workaround, not sure
> it's correlated)

That's definitely wrong. What is consuming CPU time?

> It's running OpenSuse Leap 15.2 (the bug came out when upgrading from
> 15.1, thus going from kernel 4.12 to 5.3) I suspect the same bug is
> responsible for making me switch to suse after failing to upgrade
> debian from 9 (kernel 4.9) to 10 (kernel 4.19)
>
> The workaround is to pass irqaffinity=0 on boot.
>
> Attached: dmesg output with and without the irqaffinity parameter,
> lspci output, /proc/cpuinfo contents.
>
> Let me know what else is needed.

1) You're booting with an out of tree module:

   > [   17.080069] vboxdrv: loading out-of-tree module taints kernel.

   Please reproduce without this.

2) Please provide information what is consuming 90% of a CPU

3) Please provide the output of /proc/interrupts for both boot scenarios

   Take a snapshot right after boot and another one a minute later.

Thanks,

        tglx
View attachment "dmesg_novboxdrv_clean.txt" of type "text/plain" (66803 bytes)

View attachment "dmesg_novboxdrv_irqaffinity0.txt" of type "text/plain" (100704 bytes)

View attachment "interrupts_after1min_clean.txt" of type "text/plain" (3147 bytes)

View attachment "interrupts_after1min_irqaffinity0.txt" of type "text/plain" (3147 bytes)

View attachment "interrupts_clean.txt" of type "text/plain" (3153 bytes)

View attachment "interrupts_irqaffinity0.txt" of type "text/plain" (3153 bytes)

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