Messages in this thread | | | Date | Wed, 31 Mar 2004 00:49:02 +0200 | From | Andrea Arcangeli <> | Subject | Re: route cache DoS testing and softirqs |
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On Tue, Mar 30, 2004 at 02:22:10PM -0800, David S. Miller wrote: > Otherwise, keep in mind what I said, and also as Robert mentioned every > single local_bh_enable() is going to call do_softirq() if the count falls > to zero.
I was less concerned about the do_sofitrq in local_bh_enable, since that runs in a scheduler-aware context, so at least the timeslice is definitely accounted for and it'll schedule at some point (unlike with an hardirq flood). Actually the length of the default timeslice matters too here, lowering the max timeslice to 10msec would certainly reduce the effect.
call_rcu_bh will fix the local_bh_enable too. The only problem with call_rcu_bh is how to queue the tasklets in every cpu (an IPI sounds overkill at high frequency, because effectively here we're running the rcu callbacks in a potential fast path). OTOH if we've to add a spinlock to queue the tasklet, then we might as well take a spinlock in the routing cache in the first place (at least for this workload). - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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