From: Jens Axboe <axboe@kernel.dk>
To: Sagi Grimberg <sagi@grimberg.me>, Ming Lei <ming.lei@redhat.com>
Cc: Keith Busch <kbusch@kernel.org>,
linux-block@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
linux-nvme@lists.infradead.org, Chao Leng <lengchao@huawei.com>
Subject: Re: [PATCH v3 1/2] blk-mq: add async quiesce interface
Date: Mon, 27 Jul 2020 14:37:46 -0600 [thread overview]
Message-ID: <f2fc0ecf-b599-678f-7241-fcd44cde6fab@kernel.dk> (raw)
In-Reply-To: <2c2ae567-6953-5b7f-2fa1-a65e287b5a9d@grimberg.me>
On 7/27/20 12:36 PM, Sagi Grimberg wrote:
>
>>>>> +void blk_mq_quiesce_queue_async(struct request_queue *q)
>>>>> +{
>>>>> + struct blk_mq_hw_ctx *hctx;
>>>>> + unsigned int i;
>>>>> +
>>>>> + blk_mq_quiesce_queue_nowait(q);
>>>>> +
>>>>> + queue_for_each_hw_ctx(q, hctx, i) {
>>>>> + init_completion(&hctx->rcu_sync.completion);
>>>>> + init_rcu_head(&hctx->rcu_sync.head);
>>>>> + if (hctx->flags & BLK_MQ_F_BLOCKING)
>>>>> + call_srcu(hctx->srcu, &hctx->rcu_sync.head,
>>>>> + wakeme_after_rcu);
>>>>> + else
>>>>> + call_rcu(&hctx->rcu_sync.head,
>>>>> + wakeme_after_rcu);
>>>>> + }
>>>>
>>>> Looks not necessary to do anything in case of !BLK_MQ_F_BLOCKING, and single
>>>> synchronize_rcu() is OK for all hctx during waiting.
>>>
>>> That's true, but I want a single interface for both. v2 had exactly
>>> that, but I decided that this approach is better.
>>
>> Not sure one new interface is needed, and one simple way is to:
>>
>> 1) call blk_mq_quiesce_queue_nowait() for each request queue
>>
>> 2) wait in driver specific way
>>
>> Or just wondering why nvme doesn't use set->tag_list to retrieve NS,
>> then you may add per-tagset APIs for the waiting.
>
> Because it puts assumptions on how quiesce works, which is something
> I'd like to avoid because I think its cleaner, what do others think?
> Jens? Christoph?
I'd prefer to have it in a helper, and just have blk_mq_quiesce_queue()
call that.
--
Jens Axboe
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next prev parent reply other threads:[~2020-07-27 20:38 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-26 0:22 [PATCH v3 0/2] improve quiesce time for large amount of namespaces Sagi Grimberg
2020-07-26 0:23 ` [PATCH v3 1/2] blk-mq: add async quiesce interface Sagi Grimberg
2020-07-26 9:31 ` Ming Lei
2020-07-26 16:27 ` Sagi Grimberg
2020-07-27 2:08 ` Ming Lei
2020-07-27 3:33 ` Chao Leng
2020-07-27 3:50 ` Ming Lei
2020-07-27 5:55 ` Chao Leng
2020-07-27 6:32 ` Ming Lei
2020-07-27 18:40 ` Sagi Grimberg
2020-07-27 18:38 ` Sagi Grimberg
2020-07-27 18:36 ` Sagi Grimberg
2020-07-27 20:37 ` Jens Axboe [this message]
2020-07-27 21:00 ` Sagi Grimberg
2020-07-27 21:05 ` Jens Axboe
2020-07-27 21:21 ` Keith Busch
2020-07-27 21:30 ` Jens Axboe
2020-07-28 1:09 ` Ming Lei
2020-07-26 0:23 ` [PATCH v3 2/2] nvme: improve quiesce time for large amount of namespaces Sagi Grimberg
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