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Subject: Re: [PATCH -next 00/11] support concurrent sync io for bfq on a
 specail occasion
From:   Paolo Valente <paolo.valente@linaro.org>
In-Reply-To: <11fda851-a552-97ea-d083-d0288c17ba53@huawei.com>
Date:   Fri, 18 Mar 2022 13:38:35 +0100
Cc:     Tejun Heo <tj@kernel.org>, Jens Axboe <axboe@kernel.dk>,
        Jan Kara <jack@suse.cz>, cgroups@vger.kernel.org,
        linux-block <linux-block@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, yi.zhang@huawei.com
Content-Transfer-Encoding: quoted-printable
Message-Id: <1AE1457D-AAE1-4A13-8593-451E9396028A@linaro.org>
References: <20220305091205.4188398-1-yukuai3@huawei.com>
 <e299180e-cdbd-0837-8478-5e397ac8166b@huawei.com>
 <11fda851-a552-97ea-d083-d0288c17ba53@huawei.com>
To:     "yukuai (C)" <yukuai3@huawei.com>
Precedence: bulk

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@huawei.com> =
ha scritto:
>=20
> friendly ping ...
>=20
> =E5=9C=A8 2022/03/11 14:31, yukuai (C) =E5=86=99=E9=81=93:
>> friendly ping ...
>> =E5=9C=A8 2022/03/05 17:11, Yu Kuai =E5=86=99=E9=81=93:
>>> 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().
>>>=20
>>> This patchset tries to support concurrent sync io if all the sync =
ios
>>> are issued from the same cgroup:
>>>=20
>>> 1) Count root_group into 'num_groups_with_pending_reqs', patch 1-5;
>>>=20
>>> 2) Don't idle if 'num_groups_with_pending_reqs' is 1, patch 6;
>>>=20
>>> 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;
>>>=20
>>> 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.
>>>=20
>>> 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;
>>>=20
>>> 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.
>>>=20
>>> fio test script: startdelay is used to avoid queue merging
>>> [global]
>>> filename=3D/dev/nvme0n1
>>> allow_mounted_write=3D0
>>> ioengine=3Dpsync
>>> direct=3D1
>>> ioscheduler=3Dbfq
>>> offset_increment=3D10g
>>> group_reporting
>>> rw=3Drandwrite
>>> bs=3D4k
>>>=20
>>> [test1]
>>> numjobs=3D1
>>>=20
>>> [test2]
>>> startdelay=3D1
>>> numjobs=3D1
>>>=20
>>> [test3]
>>> startdelay=3D2
>>> numjobs=3D1
>>>=20
>>> [test4]
>>> startdelay=3D3
>>> numjobs=3D1
>>>=20
>>> [test5]
>>> startdelay=3D4
>>> numjobs=3D1
>>>=20
>>> [test6]
>>> startdelay=3D5
>>> numjobs=3D1
>>>=20
>>> [test7]
>>> startdelay=3D6
>>> numjobs=3D1
>>>=20
>>> [test8]
>>> startdelay=3D7
>>> numjobs=3D1
>>>=20
>>> test result:
>>> running fio on root cgroup
>>> v5.17-rc6:       550 Mib/s
>>> v5.17-rc6-patched: 550 Mib/s
>>>=20
>>> running fio on non-root cgroup
>>> v5.17-rc6:       349 Mib/s
>>> v5.17-rc6-patched: 550 Mib/s
>>>=20
>>> 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()
>>>=20
>>>   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(-)
>>>=20