linux-kernel - Re: [PATCH -next 00/11] support concurrent sync io for bfq on a specail occasion

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Date:   Fri, 18 Mar 2022 13:38:35 +0100
From:   Paolo Valente <paolo.valente@...aro.org>
To:     "yukuai (C)" <yukuai3@...wei.com>
Cc:     Tejun Heo <tj@...nel.org>, Jens Axboe <axboe@...nel.dk>,
        Jan Kara <jack@...e.cz>, cgroups@...r.kernel.org,
        linux-block <linux-block@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, yi.zhang@...wei.com
Subject: Re: [PATCH -next 00/11] support concurrent sync io for bfq on a
 specail occasion

Hi,
could you please add pointers to the thread(s) where we have already revised this series (if we have). I don't see any reference to that in this cover letter.

Paolo

> Il giorno 17 mar 2022, alle ore 02:49, yukuai (C) <yukuai3@...wei.com> ha scritto:
> 
> friendly ping ...
> 
> 在 2022/03/11 14:31, yukuai (C) 写道:
>> friendly ping ...
>> 在 2022/03/05 17:11, Yu Kuai 写道:
>>> 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().
>>> 
>>> This patchset tries to support concurrent sync io if all the sync ios
>>> are issued from the same cgroup:
>>> 
>>> 1) Count root_group into 'num_groups_with_pending_reqs', patch 1-5;
>>> 
>>> 2) Don't idle if 'num_groups_with_pending_reqs' is 1, patch 6;
>>> 
>>> 3) Don't count the group if the group doesn't have pending requests,
>>> while it's child groups may have pending requests, patch 7;
>>> 
>>> This is because, for example:
>>> if sync ios are issued from cgroup /root/c1/c2, root, c1 and c2
>>> will all be counted into 'num_groups_with_pending_reqs',
>>> which makes it impossible to handle sync ios concurrently.
>>> 
>>> 4) Decrease 'num_groups_with_pending_reqs' when the last queue completes
>>> all the requests, while child groups may still have pending
>>> requests, patch 8-10;
>>> 
>>> This is because, for example:
>>> 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.
>>> After t1 stopped, num_groups_with_pending_reqs is still 2. sync io from
>>> t2 and t3 still can't be handled concurrently.
>>> 
>>> fio test script: startdelay is used to avoid queue merging
>>> [global]
>>> filename=/dev/nvme0n1
>>> 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
>>> v5.17-rc6:       550 Mib/s
>>> v5.17-rc6-patched: 550 Mib/s
>>> 
>>> running fio on non-root cgroup
>>> v5.17-rc6:       349 Mib/s
>>> v5.17-rc6-patched: 550 Mib/s
>>> 
>>> Yu Kuai (11):
>>>    block, bfq: add new apis to iterate bfq entities
>>>    block, bfq: apply news apis where root group is not expected
>>>    block, bfq: cleanup for __bfq_activate_requeue_entity()
>>>    block, bfq: move the increasement of 'num_groups_with_pending_reqs' to
>>>      it's caller
>>>    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 parent bfqg when bfqq is activated
>>>    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: cleanup bfqq_group()
>>> 
>>>   block/bfq-cgroup.c  | 13 +++----
>>>   block/bfq-iosched.c | 87 +++++++++++++++++++++++----------------------
>>>   block/bfq-iosched.h | 41 +++++++++++++--------
>>>   block/bfq-wf2q.c    | 56 +++++++++++++++--------------
>>>   4 files changed, 106 insertions(+), 91 deletions(-)
>>>