Messages in this thread | | | Date | Fri, 24 Feb 2012 10:08:05 +0800 | From | Michael Wang <> | Subject | Re: [PATCH v5] sched: Avoid unnecessary work in reweight_entity |
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On 02/23/2012 06:40 PM, Michael Wang wrote:
> On 02/20/2012 09:08 PM, Peter Zijlstra wrote: > > Hi, Peter > > Sorry for reply so late, I was blocked by some issue army while setup the > testing environment. > >> On Sat, 2012-02-18 at 09:43 +0800, Michael Wang wrote: >>> And as reight_entity is invoked very often, I think this patch can do some help to the >>> performance, although there are no numbers, we can prove it logically :) >> >> Well, you're probably right (although I think you completely ignored the >> optimizing compiler), but still it would be good to get some numbers to >> confirm reality :-) > > > That's right, if consider the compiler's optimization, the logic improvements > I listed may not be true... > >> > >> Just pick your favourite cgroup workload/benchmark and run a pre/post >> comparison, possible using perf record. >> >> If all squares up you should see an improvement in your benchmark score >> as well as see a reduction in time spend in the function you're >> patching. > > > So I created a cpuset cgroup 'rg1' and his sub memory group 'sub', > attached current shell to 'sub', then use 'time make kernel' as benchmark. > > Below is the test result: > > 'time make': > old > real: 87m53.804s user: 66m41.886s sys: 11m51.792s > new > real: 86m8.485s user: 65m49.211s sys: 11m47.264s > > 'time make -j14': > old: > real: 42m43.825s user: 124m13.726s sys: 17m57.183s > new > real: 39m0.072s user: 114m33.258s sys: 15m30.662s >
Hi, Peter
Someone notify me that this result is ridiculous, I should have done more test, not just once, this is really my fault, please give me more time, I will back with more data so we can use average number.
Regards, Michael Wang
> I also try to use 'perf sched record', but I can only record few seconds time, > otherwise it will be too big and report some error, as the record time is too > short, results are very different from each other, I failed to use them to prove > the patch:( > > I also have try to use some other method, I moved 'reweight_entity' and related > functions to user space, and invoke it 10000000 times in 'main', I have append > part of the code (really raw...) in the end. > > Three times output is: > > old: > real 0m0.715s 0m0.710s 0m0.739s > user 0m0.716s 0m0.708s 0m0.736s > sys 0m0.000s 0m0.000s 0m0.000s > > new: > real 0m0.318s 0m0.308s 0m0.317s > user 0m0.316s 0m0.304s 0m0.316s > sys 0m0.000s 0m0.000s 0m0.000s > > It seems like that new code can save more then half execution time, but also we > can see, after calculation, what I have done can only save 0.04ns(too small...). > > The user space test result is not accurate but at least we can know new code is > faster then old. > > Please tell me if we need to do some thing else, and thanks for your suggestion :) > > Regards, > Michael Wang > > > > User space code: > > void > account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) > { > update_load_add(&cfs_rq->load, se->load.weight); > if (1) > update_load_add(&cfs_rq->load, se->load.weight); > if (1) { > add_cfs_task_weight(cfs_rq, se->load.weight); > list_add(&se->group_node, &cfs_rq->tasks); > } > cfs_rq->nr_running++; > } > > void > account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se) > { > update_load_sub(&cfs_rq->load, se->load.weight); > if (1) > update_load_sub(&cfs_rq->load, se->load.weight); > if (1) { > add_cfs_task_weight(cfs_rq, -se->load.weight); > list_del_init(&se->group_node); > } > cfs_rq->nr_running--; > } > > void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, > unsigned long weight) > { > if (1) { > account_entity_dequeue(cfs_rq, se); > } > > update_load_set(&se->load, weight); > > if (1) > account_entity_enqueue(cfs_rq, se); > } > > void reweight_entity_new(struct cfs_rq *cfs_rq, struct sched_entity *se, > unsigned long weight) > { > if (1) { > update_load_add(&cfs_rq->load, weight - se->load.weight); > if(1) > update_load_add(&cfs_rq->load, weight - > se->load.weight); > if(1) > add_cfs_task_weight(cfs_rq, weight > -se->load.weight); > } > update_load_set(&se->load, weight); > } > > int main() > { > struct cfs_rq cfsrq; > struct sched_entity se; > memset(&cfsrq, 0, sizeof(struct cfs_rq)); > memset(&se, 0, sizeof(struct sched_entity)); > INIT_LIST_HEAD(&se.group_node); > INIT_LIST_HEAD(&cfsrq.tasks); > int i = 10000000; > while(i) { > i--; > reweight_entity_new(&cfsrq, &se, 10); > //reweight_entity(&cfsrq, &se, 10); > } > } > >> -- >> 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/ >> > > > > > > > > > -- > 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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