Messages in this thread | | | Subject | Re: [PATCH -next 10/11] block, bfq: decrease 'num_groups_with_pending_reqs' earlier | From | "yukuai (C)" <> | Date | Fri, 15 Apr 2022 09:10:06 +0800 |
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在 2022/04/13 19:40, yukuai (C) 写道: > 在 2022/04/13 19:28, Jan Kara 写道: >> On Sat 05-03-22 17:12:04, Yu Kuai wrote: >>> Currently 'num_groups_with_pending_reqs' won't be decreased when >>> the group doesn't have any pending requests, while some child group >>> still have pending requests. The decrement is delayed to when all the >>> child groups doesn't have any pending requests. >>> >>> For example: >>> 1) t1 issue sync io on root group, t2 and t3 issue sync io on the same >>> child group. num_groups_with_pending_reqs is 2 now. >>> 2) t1 stopped, num_groups_with_pending_reqs is still 2. io from t2 and >>> t3 still can't be handled concurrently. >>> >>> Fix the problem by decreasing 'num_groups_with_pending_reqs' >>> immediately upon the weights_tree removal of last bfqq of the group. >>> >>> Signed-off-by: Yu Kuai <yukuai3@huawei.com> >> >> So I'd find the logic easier to follow if you completely removed >> entity->in_groups_with_pending_reqs and did updates of >> bfqd->num_groups_with_pending_reqs like: >> >> if (!bfqg->num_entities_with_pending_reqs++) >> bfqd->num_groups_with_pending_reqs++; >> > Hi, > > Indeed, this is an excellent idle, and much better than the way I did. > > Thanks, > Kuai > >> and similarly on the remove side. And there would we literally two places >> (addition & removal from weight tree) that would need to touch these >> counters. Pretty obvious and all can be done in patch 9. >> >> Honza Hi, Jan
I think with this change, we can count root_group while activating bfqqs that are under root_group, thus there is no need to modify for_each_entity(or fake bfq_sched_data) any more.
The special case is that weight racing bfqqs are not inserted into weights tree, and I think this can be handled by adding a fake bfq_weight_counter for such bfqqs.
What do you think ?
Kuai
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