On Thu 28-04-22 19:19:06, Yu Kuai wrote: > Currently, bfq can't handle sync io concurrently as long as they > are not issued from root group. This is because > 'bfqd->num_groups_with_pending_reqs > 0' is always true in > bfq_asymmetric_scenario(). > > The way that bfqg is counted into 'num_groups_with_pending_reqs': > > Before this patch: > 1) root group will never be counted. > 2) Count if bfqg or it's child bfqgs have pending requests. > 3) Don't count if bfqg and it's child bfqgs complete all the requests. > > After this patch: > 1) root group is counted. > 2) Count if bfqg have at least one bfqq that is marked busy. > 3) Don't count if bfqg doesn't have any busy bfqqs. > > The main reason to use busy state of bfqq instead of 'pending requests' > is that bfqq can stay busy after dispatching the last request if idling > is needed for service guarantees. > > With this change, the occasion that only one group is activated can be > detected, and next patch will support concurrent sync io in the > occasion. > > This patch also rename 'num_groups_with_pending_reqs' to > 'num_groups_with_busy_queues'. > > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx> > --- > block/bfq-iosched.c | 46 ++----------------------------------- > block/bfq-iosched.h | 55 ++++++--------------------------------------- > block/bfq-wf2q.c | 19 ++++------------ > 3 files changed, 13 insertions(+), 107 deletions(-) I love the diffstat :) > + * Number of groups with at leaset one bfqq that is marked busy, ^^^^^ least Otherwise the patch looks good so feel free to add: Reviewed-by: Jan Kara <jack@xxxxxxx> Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
