Bfq can't handle sync io concurrently as long as the io are not issued from root group currently. Previous patch set: https://lore.kernel.org/lkml/20211014014556.3597008-2-yukuai3@xxxxxxxxxx/t/ During implemting the method mentioned by the above patch set, I found more problems that will block implemting concurrent sync io. The modifications of this patch set are as follows: 1) count root group into 'num_groups_with_pending_reqs'; 2) don't idle if 'num_groups_with_pending_reqs' is 1; 3) If the group doesn't have pending requests while it's child groups have pending requests, don't count the group. 4) Once the group doesn't have pending requests, decrease 'num_groups_with_pending_reqs' immediately. Don't delay to when all it's child groups don't have pending requests. Noted that I just tested basic functionality of this patchset, and I think it's better to see if anyone have suggestions or better solutions. Yu Kuai (9): block, bfq: add new apis to iterate bfq entities block, bfq: apply news apis where root group is not expected block, bfq: handle the case when for_each_entity() access root group block, bfq: count root group into 'num_groups_with_pending_reqs' block, bfq: do not idle if only one cgroup is activated block, bfq: only count group that the bfq_queue belongs to block, bfq: record how many queues have pending requests in bfq_group block, bfq: move forward __bfq_weights_tree_remove() block, bfq: decrease 'num_groups_with_pending_reqs' earlier block/bfq-cgroup.c | 3 +- block/bfq-iosched.c | 92 +++++++++++++++++++++++---------------------- block/bfq-iosched.h | 41 +++++++++++++------- block/bfq-wf2q.c | 44 +++++++++++++++------- 4 files changed, 106 insertions(+), 74 deletions(-) -- 2.31.1
