Messages in this thread | | | Date | Sat, 20 Mar 2004 18:43:16 +0530 | From | Dipankar Sarma <> | Subject | Re: CONFIG_PREEMPT and server workloads |
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On Sat, Mar 20, 2004 at 01:24:11PM +0100, Andrea Arcangeli wrote: > On Fri, Mar 19, 2004 at 10:52:03PM +0530, Dipankar Sarma wrote: > > the overall problem, IMO. I am collecting some instrumentation > > data to understand softirq/rcu behavior during heavy loads and > > ways to counter long running softirqs. > > > > Latency isn't the only issue. DoS on route cache is another > > issue that needs to be addressed. I have been experimenting > > with Robert Olsson's router test and should have some more results > > out soon. > > why don't you simply interrupt rcu_do_batch after a dozen of callbacks? > if it gets interrupted you then go ahead and you splice the remaining > entries into another list for a tasklet, then the tasklet will be a > reentrant one, so the ksoftirqd will take care of the latency. > > the only valid reason to use the timer irq instead of the tasklet in the > first place is to delay the rcu invocation and coalesce the work > together, but if there's too much work to do you must go back to the > tasklet way that has always been scheduler-friendy.
Andrea, I *am* working on a throttling mechanism for rcu/softirqs. I just didn't see the point in publishing it until I had the measurement results in hand :)
I will publish the results under both router DoS and filesystem workload.
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