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Subject: Re: [PATCH -next 00/11] support concurrent sync io for bfq on a
 specail occasion
From:   "yukuai (C)" <yukuai3@huawei.com>
To:     <tj@kernel.org>, <axboe@kernel.dk>, <paolo.valente@linaro.org>,
        <jack@suse.cz>
CC:     <cgroups@vger.kernel.org>, <linux-block@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <yi.zhang@huawei.com>
References: <20220305091205.4188398-1-yukuai3@huawei.com>
 <e299180e-cdbd-0837-8478-5e397ac8166b@huawei.com>
 <11fda851-a552-97ea-d083-d0288c17ba53@huawei.com>
 <e78fc7c5-cf08-9fc7-3f81-7ff8aaf37673@huawei.com>
 <81cfac80-83f6-7381-d4ad-560dfcdd9a9d@huawei.com>
Message-ID: <b5ee609d-e104-bc91-f0d4-21e27d411ab8@huawei.com>
Date:   Fri, 8 Apr 2022 14:50:47 +0800
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friendly ping ...

在 2022/04/01 11:43, yukuai (C) 写道:
> friendly ping ...
> 
> 在 2022/03/25 15:30, yukuai (C) 写道:
>> friendly ping ...
>>
>> 在 2022/03/17 9:49, yukuai (C) 写道:
>>> 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(-)
>>>>>