Re: [PATCH 5/5] thunderbolt: stream: Add support for busy polling

[Lukas Wunner <lukas@wunner.de>]

On Tue, Jul 28, 2026 at 01:51:41PM +0200, Mika Westerberg wrote:
> Using interrupts and scheduling workers increase latency so latency
> critical applications may want to avoid that. Make this possible in
> USB4STREAM by adding a new ConfigFS attribute: busy_poll that, when
> activated switches the rings to polling mode. The cost for lower latency
> is that this burns more CPU cycles and things like poll(2) cannot be
> used.

Hm, would it be possible to auto-detect whether polling is more performant
for the current workload and automatically enable and disable it?
E.g. by counting the number of interrupts in a given interval and
enabling/disabling polling based on a high water mark / low water mark?
Those marks could then be finetuned from user space, but moving in and
out of polling automatically would be more desirable I think.  Forcing
polling could be achieved by setting the water marks to a special value,
e.g. 0 or UINT_MAX.

Thanks,

Lukas