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SubjectRe: [RFC 1/2] softirq: Defer net rx/tx processing to ksoftirqd context
On Wed, Jan 10, 2018 at 08:19:49PM -0800, Linus Torvalds wrote:
> On Wed, Jan 10, 2018 at 7:22 PM, Frederic Weisbecker
> <frederic@kernel.org> wrote:
> >
> > Makes sense, but I think you need to keep the TASK_RUNNING check.
>
> Yes, good point.
>
> > So perhaps it should be:
> >
> > - return tsk && (tsk->state == TASK_RUNNING);
> > + return (tsk == current) && (tsk->state == TASK_RUNNING);
>
> Looks good to me - definitely worth trying.
>
> Maybe that weakens the thing so much that it doesn't actually help the
> UDP packet storm case?
>
> And maybe it's not sufficient for the dvb issue.
>
> But I think it's worth at least testing. Maybe it makes neither side
> entirely happy, but maybe it might be a good halfway point?

Yes I believe Dmitry is facing a different problem where he would rather
see ksoftirqd scheduled more often to handle the queue as a deferred batch
instead of having it served one by one on the tails of IRQ storms.
(Dmitry correct me if I misunderstood).

But your patch still seems to make sense for the case you described: when
ksoftirqd is voluntarily preempted off and the current IRQ could handle the
queue.

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