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From: "yukuai (C)" <yukuai3@huawei.com>
To: Jan Kara <jack@suse.cz>
Cc: <tj@kernel.org>, <axboe@kernel.dk>, <paolo.valente@linaro.org>,
	<cgroups@vger.kernel.org>, <linux-block@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>, <yi.zhang@huawei.com>
Subject: Re: [PATCH -next v3 2/3] block, bfq: refactor the counting of 'num_groups_with_pending_reqs'
Date: Thu, 28 Apr 2022 09:09:36 +0800	[thread overview]
Message-ID: <d36b4904-3db8-537c-5040-b496272ccf70@huawei.com> (raw)
In-Reply-To: <20220427124908.o3cl72h2uflmufso@quack3.lan>

在 2022/04/27 20:49, Jan Kara 写道:
> On Wed 27-04-22 20:47:21, Yu Kuai wrote:
>> 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 patch:
>>   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 patch:
>>   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.
>>
>> With this change, the occasion that only one group is activated can be
>> detected, and next patch will support concurrent sync io in the
>> occasion.
>>
>> This patch also rename 'num_groups_with_pending_reqs' to
>> 'num_groups_with_busy_queues'.
>>
>> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> 
> Looks good. Just I think you forgot to remove in_groups_with_pending_reqs,
> which is now unused, from bfq_entity.

Will remove it in the next iteration.

Thanks,
Kuai

WARNING: multiple messages have this Message-ID (diff)
From: "yukuai (C)" <yukuai3-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
To: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
Cc: tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
	axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org,
	paolo.valente-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org,
	cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	yi.zhang-hv44wF8Li93QT0dZR+AlfA@public.gmane.org
Subject: Re: [PATCH -next v3 2/3] block, bfq: refactor the counting of 'num_groups_with_pending_reqs'
Date: Thu, 28 Apr 2022 09:09:36 +0800	[thread overview]
Message-ID: <d36b4904-3db8-537c-5040-b496272ccf70@huawei.com> (raw)
In-Reply-To: <20220427124908.o3cl72h2uflmufso-/1kMjMImKQN+urZeOPWqwQ@public.gmane.org>

ÔÚ 2022/04/27 20:49, Jan Kara дµÀ:
> On Wed 27-04-22 20:47:21, Yu Kuai wrote:
>> 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 patch:
>>   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 patch:
>>   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.
>>
>> With this change, the occasion that only one group is activated can be
>> detected, and next patch will support concurrent sync io in the
>> occasion.
>>
>> This patch also rename 'num_groups_with_pending_reqs' to
>> 'num_groups_with_busy_queues'.
>>
>> Signed-off-by: Yu Kuai <yukuai3-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
> 
> Looks good. Just I think you forgot to remove in_groups_with_pending_reqs,
> which is now unused, from bfq_entity.

Will remove it in the next iteration.

Thanks,
Kuai

  reply	other threads:[~2022-04-28  1:09 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-27 12:47 [PATCH -next v3 0/3] support concurrent sync io for bfq on a specail occasion Yu Kuai
2022-04-27 12:47 ` Yu Kuai
2022-04-27 12:47 ` [PATCH -next v3 1/3] block, bfq: record how many queues are busy in bfq_group Yu Kuai
2022-04-27 12:47   ` Yu Kuai
2022-04-27 12:52   ` Jan Kara
2022-04-28  1:08     ` yukuai (C)
2022-04-28  1:08       ` yukuai (C)
2022-04-27 12:47 ` [PATCH -next v3 2/3] block, bfq: refactor the counting of 'num_groups_with_pending_reqs' Yu Kuai
2022-04-27 12:47   ` Yu Kuai
2022-04-27 12:49   ` Jan Kara
2022-04-27 12:49     ` Jan Kara
2022-04-28  1:09     ` yukuai (C) [this message]
2022-04-28  1:09       ` yukuai (C)
2022-04-27 12:47 ` [PATCH -next v3 3/3] block, bfq: do not idle if only one group is activated Yu Kuai
2022-04-27 12:47   ` Yu Kuai

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