Changes in v8: - Instead of using whether bfqq is busy, using whether bfqq has pending requests. As Paolo pointed out the former way is problematic. Changes in v7: - fix mismatch bfq_inc/del_busy_queues() and bfqq_add/del_bfqq_busy(), also retest this patchset on v5.18 to make sure functionality is correct. - move the updating of 'bfqd->busy_queues' into new apis Changes in v6: - add reviewed-by tag for patch 1 Changes in v5: - rename bfq_add_busy_queues() to bfq_inc_busy_queues() in patch 1 - fix wrong definition in patch 1 - fix spelling mistake in patch 2: leaset -> least - update comments in patch 3 - add reviewed-by tag in patch 2,3 Changes in v4: - split bfq_update_busy_queues() to bfq_add/dec_busy_queues(), suggested by Jan Kara. - remove unused 'in_groups_with_pending_reqs', Changes in v3: - remove the cleanup patch that is irrelevant now(I'll post it separately). - instead of hacking wr queues and using weights tree insertion/removal, using bfq_add/del_bfqq_busy() to count the number of groups (suggested by Jan Kara). Changes in v2: - Use a different approch to count root group, which is much simple. 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 patchset: 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 patchset: 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 the above changes, concurrent sync io can be supported if only one group is activated. fio test script(startdelay is used to avoid queue merging): [global] filename=/dev/sda allow_mounted_write=0 ioengine=psync direct=1 ioscheduler=bfq offset_increment=10g group_reporting rw=randwrite bs=4k [test1] numjobs=1 [test2] startdelay=1 numjobs=1 [test3] startdelay=2 numjobs=1 [test4] startdelay=3 numjobs=1 [test5] startdelay=4 numjobs=1 [test6] startdelay=5 numjobs=1 [test7] startdelay=6 numjobs=1 [test8] startdelay=7 numjobs=1 test result: running fio on root cgroup v5.18: 112 Mib/s v5.18-patched: 112 Mib/s running fio on non-root cgroup v5.18: 51.2 Mib/s v5.18-patched: 112 Mib/s Note that I also test null_blk with "irqmode=2 completion_nsec=100000000(100ms) hw_queue_depth=1", and tests show that service guarantees are still preserved. Previous versions: RFC: https://lore.kernel.org/all/20211127101132.486806-1-yukuai3@xxxxxxxxxx/ v1: https://lore.kernel.org/all/20220305091205.4188398-1-yukuai3@xxxxxxxxxx/ v2: https://lore.kernel.org/all/20220416093753.3054696-1-yukuai3@xxxxxxxxxx/ v3: https://lore.kernel.org/all/20220427124722.48465-1-yukuai3@xxxxxxxxxx/ v4: https://lore.kernel.org/all/20220428111907.3635820-1-yukuai3@xxxxxxxxxx/ v5: https://lore.kernel.org/all/20220428120837.3737765-1-yukuai3@xxxxxxxxxx/ v6: https://lore.kernel.org/all/20220523131818.2798712-1-yukuai3@xxxxxxxxxx/ v7: https://lore.kernel.org/all/20220528095020.186970-1-yukuai3@xxxxxxxxxx/ Yu Kuai (4): block, bfq: support to track if bfqq has pending requests block, bfq: record how many queues have pending requests block, bfq: refactor the counting of 'num_groups_with_pending_reqs' block, bfq: do not idle if only one group is activated block/bfq-cgroup.c | 1 + block/bfq-iosched.c | 47 +++------------------------------------------ block/bfq-iosched.h | 20 ++++++++++--------- block/bfq-wf2q.c | 47 ++++++++++++++++++++++++++++++--------------- 4 files changed, 47 insertions(+), 68 deletions(-) -- 2.31.1
