Messages in this thread | | | From | Linus Torvalds <> | Date | Thu, 11 Jan 2018 12:22:38 -0800 | Subject | Re: [RFC 1/2] softirq: Defer net rx/tx processing to ksoftirqd context |
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On Thu, Jan 11, 2018 at 12:16 PM, Eric Dumazet <edumazet@google.com> wrote: > > Note that when I implemented TCP Small queues, I did experiments between > using a work queue or a tasklet, and workqueues added unacceptable P99 > latencies, when many user threads are competing with kernel threads.
Yes.
So I think one solution might be to have a hybrid system, where we do the softirq's synchronously normally (which is what you really want for good latency).
But then fall down on a threaded model - but that fallback case should be per-softirq, not global. So if one softirq uses a lot of CPU time, that shouldn't affect the latency of other softirqs.
So maybe we could get rid of the per-cpu ksoftirqd entirely, and replace it with with per-cpu and per-softirq workqueues?
Would something like that sound sane?
Just a SMOP/SMOT (small matter of programming/testing).
Linus
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