From: Sagi Grimberg <sagi@grimberg.me>
To: paulmck@kernel.org
Cc: Ming Lei <ming.lei@redhat.com>, Christoph Hellwig <hch@lst.de>,
Jens Axboe <axboe@kernel.dk>,
linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
Chao Leng <lengchao@huawei.com>, Keith Busch <kbusch@kernel.org>,
Ming Lin <mlin@kernel.org>
Subject: Re: [PATCH v5 1/2] blk-mq: add tagset quiesce interface
Date: Tue, 28 Jul 2020 21:37:23 -0700 [thread overview]
Message-ID: <57f76f9c-6fb9-b6f1-ba85-1594755e60f3@grimberg.me> (raw)
In-Reply-To: <20200729041004.GV9247@paulmck-ThinkPad-P72>
>>>> Dynamically allocating each one is possible but not very scalable.
>>>>
>>>> The question is if there is some way, we can do this with on-stack
>>>> or a single on-heap rcu_head or equivalent that can achieve the same
>>>> effect.
>>>
>>> If the hctx structures are guaranteed to stay put, you could count
>>> them and then do a single allocation of an array of rcu_head structures
>>> (or some larger structure containing an rcu_head structure, if needed).
>>> You could then sequence through this array, consuming one rcu_head per
>>> hctx as you processed it. Once all the callbacks had been invoked,
>>> it would be safe to free the array.
>>>
>>> Sounds too simple, though. So what am I missing?
>>
>> We don't want higher-order allocations...
>
> OK, I will bite... Do multiple lower-order allocations (page size is
> still lower-order, correct?) and link them together.
>
> Sorry, couldn't resist...
Possible, but I didn't want us to resort to all this complexity and
thought we can find a better, simpler solution.
WARNING: multiple messages have this Message-ID (diff)
From: Sagi Grimberg <sagi@grimberg.me>
To: paulmck@kernel.org
Cc: Jens Axboe <axboe@kernel.dk>,
linux-nvme@lists.infradead.org, Ming Lei <ming.lei@redhat.com>,
linux-block@vger.kernel.org, Chao Leng <lengchao@huawei.com>,
Keith Busch <kbusch@kernel.org>, Ming Lin <mlin@kernel.org>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v5 1/2] blk-mq: add tagset quiesce interface
Date: Tue, 28 Jul 2020 21:37:23 -0700 [thread overview]
Message-ID: <57f76f9c-6fb9-b6f1-ba85-1594755e60f3@grimberg.me> (raw)
In-Reply-To: <20200729041004.GV9247@paulmck-ThinkPad-P72>
>>>> Dynamically allocating each one is possible but not very scalable.
>>>>
>>>> The question is if there is some way, we can do this with on-stack
>>>> or a single on-heap rcu_head or equivalent that can achieve the same
>>>> effect.
>>>
>>> If the hctx structures are guaranteed to stay put, you could count
>>> them and then do a single allocation of an array of rcu_head structures
>>> (or some larger structure containing an rcu_head structure, if needed).
>>> You could then sequence through this array, consuming one rcu_head per
>>> hctx as you processed it. Once all the callbacks had been invoked,
>>> it would be safe to free the array.
>>>
>>> Sounds too simple, though. So what am I missing?
>>
>> We don't want higher-order allocations...
>
> OK, I will bite... Do multiple lower-order allocations (page size is
> still lower-order, correct?) and link them together.
>
> Sorry, couldn't resist...
Possible, but I didn't want us to resort to all this complexity and
thought we can find a better, simpler solution.
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next prev parent reply other threads:[~2020-07-29 4:37 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-27 23:10 [PATCH v5 0/2] improve nvme quiesce time for large amount of namespaces Sagi Grimberg
2020-07-27 23:10 ` Sagi Grimberg
2020-07-27 23:10 ` [PATCH v5 1/2] blk-mq: add tagset quiesce interface Sagi Grimberg
2020-07-27 23:10 ` Sagi Grimberg
2020-07-27 23:32 ` Keith Busch
2020-07-27 23:32 ` Keith Busch
2020-07-28 0:12 ` Sagi Grimberg
2020-07-28 0:12 ` Sagi Grimberg
2020-07-28 1:40 ` Ming Lei
2020-07-28 1:40 ` Ming Lei
2020-07-28 1:51 ` Jens Axboe
2020-07-28 1:51 ` Jens Axboe
2020-07-28 2:17 ` Ming Lei
2020-07-28 2:17 ` Ming Lei
2020-07-28 2:23 ` Jens Axboe
2020-07-28 2:23 ` Jens Axboe
2020-07-28 2:28 ` Ming Lei
2020-07-28 2:28 ` Ming Lei
2020-07-28 2:32 ` Jens Axboe
2020-07-28 2:32 ` Jens Axboe
2020-07-28 3:29 ` Sagi Grimberg
2020-07-28 3:29 ` Sagi Grimberg
2020-07-28 3:25 ` Sagi Grimberg
2020-07-28 3:25 ` Sagi Grimberg
2020-07-28 7:18 ` Christoph Hellwig
2020-07-28 7:18 ` Christoph Hellwig
2020-07-28 7:48 ` Sagi Grimberg
2020-07-28 7:48 ` Sagi Grimberg
2020-07-28 9:16 ` Ming Lei
2020-07-28 9:16 ` Ming Lei
2020-07-28 9:24 ` Sagi Grimberg
2020-07-28 9:24 ` Sagi Grimberg
2020-07-28 9:33 ` Ming Lei
2020-07-28 9:33 ` Ming Lei
2020-07-28 9:37 ` Sagi Grimberg
2020-07-28 9:37 ` Sagi Grimberg
2020-07-28 9:43 ` Sagi Grimberg
2020-07-28 9:43 ` Sagi Grimberg
2020-07-28 10:10 ` Ming Lei
2020-07-28 10:10 ` Ming Lei
2020-07-28 10:57 ` Christoph Hellwig
2020-07-28 10:57 ` Christoph Hellwig
2020-07-28 14:13 ` Paul E. McKenney
2020-07-28 14:13 ` Paul E. McKenney
2020-07-28 10:58 ` Christoph Hellwig
2020-07-28 10:58 ` Christoph Hellwig
2020-07-28 16:25 ` Sagi Grimberg
2020-07-28 16:25 ` Sagi Grimberg
2020-07-28 13:54 ` Paul E. McKenney
2020-07-28 13:54 ` Paul E. McKenney
2020-07-28 23:46 ` Sagi Grimberg
2020-07-28 23:46 ` Sagi Grimberg
2020-07-29 0:31 ` Paul E. McKenney
2020-07-29 0:31 ` Paul E. McKenney
2020-07-29 0:43 ` Sagi Grimberg
2020-07-29 0:43 ` Sagi Grimberg
2020-07-29 0:59 ` Keith Busch
2020-07-29 0:59 ` Keith Busch
2020-07-29 4:39 ` Sagi Grimberg
2020-07-29 4:39 ` Sagi Grimberg
2020-08-07 9:04 ` Chao Leng
2020-08-07 9:04 ` Chao Leng
2020-08-07 9:24 ` Ming Lei
2020-08-07 9:24 ` Ming Lei
2020-08-07 9:35 ` Chao Leng
2020-08-07 9:35 ` Chao Leng
2020-07-29 4:10 ` Paul E. McKenney
2020-07-29 4:10 ` Paul E. McKenney
2020-07-29 4:37 ` Sagi Grimberg [this message]
2020-07-29 4:37 ` Sagi Grimberg
2020-07-27 23:10 ` [PATCH v5 2/2] nvme: use blk_mq_[un]quiesce_tagset Sagi Grimberg
2020-07-27 23:10 ` Sagi Grimberg
2020-07-28 0:54 ` Sagi Grimberg
2020-07-28 0:54 ` Sagi Grimberg
2020-07-28 3:21 ` Chao Leng
2020-07-28 3:21 ` Chao Leng
2020-07-28 3:34 ` Sagi Grimberg
2020-07-28 3:34 ` Sagi Grimberg
2020-07-28 3:51 ` Chao Leng
2020-07-28 3:51 ` Chao Leng
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