Re: [RFC 1/2] softirq: Defer net rx/tx processing to ksoftirqd context

[Linus Torvalds]

On Fri, Jan 12, 2018 at 2:13 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Fri, Jan 12, 2018 at 06:23:08AM +0100, Mike Galbraith wrote:
>>
>> How would that be better than what RT used to do, and I still do for my
>> RT kernels via boot option, namely split ksoftirqd into per-softirq
>> threads.
>
> Since we mention it; one of the problems RT has is that all RX is
> through a single softirq context, which generates a priority inversion
> between devices.

Oh, yes, that is complete and utter shit. Not acceptable at all.

As mentioned, it really would need to be per-cpu _and_ per-softirq.

Which is why I thought workqueues might be the thing. Whatever RT is
doing is  apparently just pure and utter garbage.

             Linus