[arch-general] nvidia causing audio glitches

[Olivier Langlois]

I have a good idea of what your problem is. I had this issue long time
ago with a hpmini laptop.

The problem did end up with me sending a patch for a realteak wifi
driver.

The glitch that you hear is the symptom of the sound card interrupt not
delivered in time.

You can validate this symptom by using the ALSA command line tools such
as aplay.

You would see the error about an underflow each time that you hear a
glitch.

So what is causing this?

Usually, it is caused by a badly written driver that is masking the
interrupts for too long.

Even if the driver is masking locally the interrupts on a single core,
it will end up putting all the system interrupts to a stall because of
the round-robin interrupt balance algo, they will all end up on the
masked core pretty fast.

If possible, try to switch drivers from Nvidia to the open source one.
As a workaround, you may explore the option to pin your sound card to a
specific core to see if it helps.

Greetings,

On Wed, 2021-03-17 at 08:27 +0000, Paul Dann via arch-general wrote:
> I've had this problem ever since I got this laptop[1]: I get audio
> glitches with both pulseaudio and pipewire, through *all* audio sinks
> (built-in, USB soundcard, bluetooth). It seems to become more severe
> after a suspend/resume cycle.
> 
> I've discovered that the symptoms go away completely if I set the
> discrete NVIDIA graphics card PowerMizer setting to "Preferred Mode:
> Prefer Maximum Performance". So it seems there's something about the
> hardware's low-power behaviour that causes this.
> 
> Has anyone else experienced this? Does anyone have a clearer
> understanding of the cause? Is this something we can take to NVIDIA
> with any realistic hope of a fix?
> 
> Paul
> 
> [1] Dell Inspiron 7590, Intel Core i5-9300H, GTX 1650