On 02/29/2016 08:21 AM, Eric Dumazet wrote: > On lun., 2016-02-29 at 07:54 -0800, Peter Hurley wrote: > >> The current kernel is HZ=250 but this would occur on HZ=1000 as well. > > Right. But the problem with HZ=100 and HZ=250 is that the detection can > happens because jiffy granularity is too coarse, since > > msecs_to_jiffies(2) -> 1 > > Following patch might reduce the probability, but wont really fix your > problem. > > Fact that ksoftirqd prio is not what you want is completely orthogonal. > > diff --git a/kernel/softirq.c b/kernel/softirq.c > index 479e443..f7cc594 100644 > --- a/kernel/softirq.c > +++ b/kernel/softirq.c > @@ -180,7 +180,7 @@ EXPORT_SYMBOL(__local_bh_enable_ip); > > /* > * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times, > - * but break the loop if need_resched() is set or after 2 ms. > + * but break the loop if need_resched() is set or after 2 ms/ticks. > * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in > * certain cases, such as stop_machine(), jiffies may cease to > * increment and so we need the MAX_SOFTIRQ_RESTART limit as > @@ -191,7 +191,7 @@ EXPORT_SYMBOL(__local_bh_enable_ip); > * we want to handle softirqs as soon as possible, but they > * should not be able to lock up the box. > */ > -#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2) > +#define MAX_SOFTIRQ_TIME (1 + msecs_to_jiffies(2)) > #define MAX_SOFTIRQ_RESTART 10 > > #ifdef CONFIG_TRACE_IRQFLAGS While I appreciate the attempt, that's not the problem. Just to be clear if (time_before(jiffies, end) && !need_resched() && --max_restart) goto restart; aborts softirq *even if 0ns have elapsed*, if NET_RX has woken a process. -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
