> Il giorno 10 dic 2021, alle ore 10:50, yukuai (C) <yukuai3@xxxxxxxxxx> ha scritto: > > 在 2021/12/10 17:20, Paolo Valente 写道: >>> Il giorno 27 nov 2021, alle ore 11:11, Yu Kuai <yukuai3@xxxxxxxxxx> ha scritto: >>> >>> 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. >> Why don't yo count the parent group? It seems to me that we should count it. > Hi, Paolo > > For example, we only issue io in child group c2(root->c1->c2), > 'num_groups_with_pending_reqs' will end up greater than 1, thus it's > impossible to handle sync io concurrently. Thus I don't count root and > c1, only count c2. Right! Please explain this clearly in comments. >>> 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. >>> >> I guess this action is related to 3). > Yes, if c1, c2 are both active, and then c1 don't have any pending reqs, > I want to decrease num_groups_with_pending_reqs to 1 immediately. I'll check this point directly on the patch that does this decrement, because something is not clear to me. Thanks, Paolo > So > that sync io on c2 can be handled concurrently. > > Thanks, > Kuai > >> Thanks, >> Paolo >>> 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 >>> >> .
