Vivek Goyal wrote:> On Tue, Jun 23, 2009 at 02:44:08PM +0800, Gui Jianfeng wrote:>> Vivek Goyal wrote:>>> On Mon, Jun 22, 2009 at 03:44:08PM +0800, Gui Jianfeng wrote:>>>> Preempt the ongoing non-rt ioq if there are rt ioqs waiting for dispatching>>>> in ancestor or sibling groups. It will give other group's rt ioq an chance >>>> to dispatch ASAP.>>>>>>> Hi Gui,>>>>>> Will new preempton logic of traversing up the hiearchy so that both new>>> queue and old queue are at same level to take a preemption decision not>>> take care of above scenario?>> Hi Vivek,>>>> Would you explain a bit what do you mean about "both new queue and old queue >> are at same level to take a preemption decision". I don't understand it well.>>> > Consider following hierarchy.> > root> / | > A 1 > | > 2 > In the above diagram, A is the group and "1" and "2" are two io queues > associated with tasks.> > Now assume that queue "1" is being served and queue "2" gets backlogged.> Should queue 2 preempt queue 1 now?> > To take that decision, we need to do the comparision between type of> entity of group A and queue 1 (That is at the same level or IOW, the> entities in question have the same parent). If group A is of class RT and> queue 1 is of type BE then queue 2 should preempt queue 1 otherwise not.> > Hence in hierarchical setups to take a preemption decision, comparison> should be done at same level. So what bfq_find_matching_entity has done is going to figure out the same level entities， in turn, taking the decision. > >>> Please have a look at bfq_find_matching_entity().>>>>>> At the same time we probably don't want to preempt the non-rt queue>>> with an RT queue in sibling group until and unless sibling group is an>>> RT group.>>>>>> root>>> / \>>> BEgrpA BEgrpB>>> | | >>> BEioq1 RTioq2>>>>>> Above we got two BE group A and B and assume ioq in group A is being>>> served and then an RT request in group B comes. Because group B is an>>> BE class group, we should not preempt the queue in group A.>> Yes, i also have this concern. So, it does not allow non-rt group preempts>> another group. I'll check whether there is a way to address this issue.>>> > So here also assume ioq1 is being served and ioq2 gets backlogged. To> decide whether ioq2 should preempt ioq1 or not, one needs to go up the > hiearchy till two paths share the parent. That means one needs to go up> at the BEgrpA and BEgrpB level where they have common parent "root". Now> both the groups are of class BE hence ioq2 should not preempt ioq1.> > Hope it helps. Thanks, it's very helpful. I have a thought now. Whether we can maintain a rt ioq list in efqd, and elv_fq_select_ioq() travels this list to take preemtion decision for each available rt ioqs at the same level(by using bfq_find_matching_entity). I'd like to try it out. > > Thanks> Vivek> > > -- RegardsGui Jianfeng _______________________________________________Containers mailing listContainers@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx://lists.linux-foundation.org/mailman/listinfo/containers
