On Tue, 2016-05-10 at 14:31 -0700, Eric Dumazet wrote: > On Tue, 2016-05-10 at 14:09 -0700, Eric Dumazet wrote: > > > > On Tue, May 10, 2016 at 1:46 PM, Hannes Frederic Sowa > > <han...@stressinduktion.org> wrote: > > > > > > > > I agree here, but I don't think this patch particularly is a lot > > > of > > > bloat and something very interesting people can play with and > > > extend upon. > > > > > Sure, very rarely patch authors think their stuff is bloat. > > > > I prefer to fix kernel softirq.c, or at least show me that you > > tried > > hard enough. > > > > I am pretty sure that the following would work : > > > > When ksoftirqd is scheduled, remember this in a per cpu variable > > (ksoftiqd_scheduled) > > > > When enabling BH , do not call do_softirq() if this variable is > > set. > > > > ksoftirqd would clear the variable at the right place (probably in > > run_ksoftirqd()) > > > > Sure, this might add a lot of latency regressions, but lets fix > > them. > Only to give the idea (it is completely untested and probably buggy) > > diff --git a/kernel/softirq.c b/kernel/softirq.c > index 17caf4b63342..cb30cfd76687 100644 > --- a/kernel/softirq.c > +++ b/kernel/softirq.c > @@ -56,6 +56,7 @@ EXPORT_SYMBOL(irq_stat); > static struct softirq_action softirq_vec[NR_SOFTIRQS] > __cacheline_aligned_in_smp; > > DEFINE_PER_CPU(struct task_struct *, ksoftirqd); > +DEFINE_PER_CPU(bool, ksoftirqd_scheduled); > > const char * const softirq_to_name[NR_SOFTIRQS] = { > "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "BLOCK_IOPOLL", > @@ -73,8 +74,10 @@ static void wakeup_softirqd(void) > /* Interrupts are disabled: no need to stop preemption */ > struct task_struct *tsk = __this_cpu_read(ksoftirqd); > > - if (tsk && tsk->state != TASK_RUNNING) > + if (tsk && tsk->state != TASK_RUNNING) { > + __this_cpu_write(ksoftirqd_scheduled, true); > wake_up_process(tsk); > + } > } > > /* > @@ -162,7 +165,9 @@ void __local_bh_enable_ip(unsigned long ip, > unsigned int cnt) > */ > preempt_count_sub(cnt - 1); > > - if (unlikely(!in_interrupt() && local_softirq_pending())) { > + if (unlikely(!in_interrupt() && > + local_softirq_pending() && > + !__this_cpu_read(ksoftirqd_scheduled))) { > /* >
You might need another one of these in invoke_softirq() -- All Rights Reversed.
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