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

[Linus Torvalds]

On Wed, Jan 17, 2018 at 1:54 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> raise_softirq() -> raise_softirq_irqoff()
>
>         set_softirq_bit();
>
>         if (!in_interrupt())
>                 wake_softirqd();
>
> So if the caller is not in hard or soft interrupt context, which includes
> bottom half disabled regions softirqd is woken.

That does seem unnecessarily expensive, and maybe we could just do it
with thread flag (TIF_NOTIFY_RESUME or whatever).

In fact, that was what I *thought* we did. Maybe I just remember some
historical behavior.

Since networking seems to largely prefer softirqd anyway, maybe that
wake_softirqd() is the right thing to do anyway.

             Linus