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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>
Message-ID: <81cfac80-83f6-7381-d4ad-560dfcdd9a9d@huawei.com>
Date:   Fri, 1 Apr 2022 11:43:09 +0800
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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(-)
>>>>