On Wed, Jan 17, 2018 at 10:07 AM, Frederic Weisbecker <frede...@kernel.org> wrote: > > I see, so you may want to test (possibly much) higher values of > MAX_SOFTIRQ_RESTART, > such as 50 or 100.
I suspect the "number of softiqs per jiffy" is hardly interesting at all. We used to allow up to 2mS or ten iterations per _invocation_, never mind per timer tick. I thought you were going to actally account for time, but I don't think you ended up doing that. Maybe time isn't necessarily the thing to do, but just pure "count per jiffy" seems very bad. What I might suggest using instead: - do it by time. This may be too expensive, though. Keeping track of ns-level timing per invocation can be nasty. - do it by "we got a new softirq event while handling another softirq event". That was our old count per invocation, except you could do it per softirq, and just allow *one* (ie keep a bitmask of "I've already handled this softirq", and if the restart results in it being triggered *again* you say "ok, I'll just move this to a workqueue" - .. something else? I'd suggest trying the "if we get a new softirq event that we've already seen while we were already handling softirq events" thing. That should really take care of the networking case of "90% time spend in softirq handling during packet storms" thing. If we spend that much time on softirqs, we *will* get a new softirq while handling an old one occasionally. Linus