From: Sagi Grimberg <sagi@grimberg.me>
To: Chao Leng <lengchao@huawei.com>, Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org,
Lai Jiangshan <jiangshanlai@gmail.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
Josh Triplett <josh@joshtriplett.org>,
Bart Van Assche <bvanassche@acm.org>,
Johannes Thumshirn <Johannes.Thumshirn@wdc.com>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] blk-mq: implement queue quiesce via percpu_ref for BLK_MQ_F_BLOCKING
Date: Tue, 25 Aug 2020 10:38:43 -0700 [thread overview]
Message-ID: <6cef7a24-f19c-a39a-abd8-2f0ea50fb7a2@grimberg.me> (raw)
In-Reply-To: <399888c3-71e6-625e-3b0d-025ccbad4fd1@huawei.com>
>>>> Good, but I'd also won't want to get this without making sure the async
>>>> quiesce works well on large number of namespaces (the reason why this
>>>> is proposed in the first place). Not sure who is planning to do that...
>>>
>>> That can be added when async quiesce is done.
>>
>> Chao, are you looking into that? I'd really hate to find out we have an
>> issue there post conversion...
>
> Now we config CONFIG_TREE_SRCU, the size of TREE_SRCU is too big. I
> really appreciate the work of Ming.
>
> I review the patch, I think the patch may work well now, but do extra
> works for exception scenario. Percpu_ref is not disigned for
> serialization which read low cost. If we replace SRCU with percpu_ref,
> the benefit is save memory for blocking queue, the price is limit future
> changes or do more extra works.
>
> I do not think replace SRCU with percpu_ref is a good idea, because it's
> hard to predict how much we'll lose.
Not sure I understand your point, can you clarify what is the poor
design of percpu_ref and for which use-case?
next prev parent reply other threads:[~2020-08-25 17:38 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-20 3:02 [PATCH] blk-mq: implement queue quiesce via percpu_ref for BLK_MQ_F_BLOCKING Ming Lei
2020-08-21 6:34 ` Christoph Hellwig
2020-08-21 10:16 ` Ming Lei
2020-08-21 14:46 ` Jens Axboe
2020-08-21 15:05 ` Jens Axboe
2020-08-21 20:14 ` Sagi Grimberg
2020-08-22 13:39 ` Ming Lei
2020-08-24 8:19 ` Sagi Grimberg
2020-08-24 10:40 ` Ming Lei
2020-08-24 21:34 ` Sagi Grimberg
2020-08-25 2:32 ` Ming Lei
2020-08-25 5:24 ` Sagi Grimberg
2020-08-25 9:41 ` Chao Leng
2020-08-25 17:38 ` Sagi Grimberg [this message]
2020-08-26 7:25 ` Chao Leng
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