From: Sagi Grimberg <sagi@grimberg.me>
To: Ming Lei <ming.lei@redhat.com>
Cc: 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>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v5 1/2] blk-mq: add tagset quiesce interface
Date: Mon, 27 Jul 2020 20:25:32 -0700 [thread overview]
Message-ID: <65634c0a-4f40-ddba-2dbd-6902b902abeb@grimberg.me> (raw)
In-Reply-To: <20200728014038.GA1305646@T590>
>> drivers that have shared tagsets may need to quiesce potentially a lot
>> of request queues that all share a single tagset (e.g. nvme). Add an interface
>> to quiesce all the queues on a given tagset. This interface is useful because
>> it can speedup the quiesce by doing it in parallel.
>>
>> For tagsets that have BLK_MQ_F_BLOCKING set, we use call_srcu to all hctxs
>> in parallel such that all of them wait for the same rcu elapsed period with
>> a per-hctx heap allocated rcu_synchronize. for tagsets that don't have
>> BLK_MQ_F_BLOCKING set, we simply call a single synchronize_rcu as this is
>> sufficient.
>>
>> Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
>> ---
>> block/blk-mq.c | 66 ++++++++++++++++++++++++++++++++++++++++++
>> include/linux/blk-mq.h | 4 +++
>> 2 files changed, 70 insertions(+)
>>
>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index abcf590f6238..c37e37354330 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -209,6 +209,42 @@ void blk_mq_quiesce_queue_nowait(struct request_queue *q)
>> }
>> EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
>>
>> +static void blk_mq_quiesce_blocking_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) {
>> + WARN_ON_ONCE(!(hctx->flags & BLK_MQ_F_BLOCKING));
>> + hctx->rcu_sync = kmalloc(sizeof(*hctx->rcu_sync), GFP_KERNEL);
>> + if (!hctx->rcu_sync)
>> + continue;
>
> This approach of quiesce/unquiesce tagset is good abstraction.
I'm thinking I don't want to use this interface, it quiesce the
connect_q hctxs as well and then I need to unquiesce them which is
awkward...
> Just one more thing, please allocate a rcu_sync array because hctx is supposed
> to not store scratch stuff.
Sorry, I object to any interface that returns back the rcu_sync
allocation. Its just awkward. really..
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next prev parent reply other threads:[~2020-07-28 3:25 UTC|newest]
Thread overview: 40+ 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 ` [PATCH v5 1/2] blk-mq: add tagset quiesce interface Sagi Grimberg
2020-07-27 23:32 ` Keith Busch
2020-07-28 0:12 ` Sagi Grimberg
2020-07-28 1:40 ` Ming Lei
2020-07-28 1:51 ` Jens Axboe
2020-07-28 2:17 ` Ming Lei
2020-07-28 2:23 ` Jens Axboe
2020-07-28 2:28 ` Ming Lei
2020-07-28 2:32 ` Jens Axboe
2020-07-28 3:29 ` Sagi Grimberg
2020-07-28 3:25 ` Sagi Grimberg [this message]
2020-07-28 7:18 ` Christoph Hellwig
2020-07-28 7:48 ` Sagi Grimberg
2020-07-28 9:16 ` Ming Lei
2020-07-28 9:24 ` Sagi Grimberg
2020-07-28 9:33 ` Ming Lei
2020-07-28 9:37 ` Sagi Grimberg
2020-07-28 9:43 ` Sagi Grimberg
2020-07-28 10:10 ` Ming Lei
2020-07-28 10:57 ` Christoph Hellwig
2020-07-28 14:13 ` Paul E. McKenney
2020-07-28 10:58 ` Christoph Hellwig
2020-07-28 16:25 ` Sagi Grimberg
2020-07-28 13:54 ` Paul E. McKenney
2020-07-28 23:46 ` Sagi Grimberg
2020-07-29 0:31 ` Paul E. McKenney
2020-07-29 0:43 ` Sagi Grimberg
2020-07-29 0:59 ` Keith Busch
2020-07-29 4:39 ` Sagi Grimberg
2020-08-07 9:04 ` Chao Leng
2020-08-07 9:24 ` Ming Lei
2020-08-07 9:35 ` Chao Leng
2020-07-29 4:10 ` Paul E. McKenney
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
2020-07-28 0:54 ` Sagi Grimberg
2020-07-28 3:21 ` Chao Leng
2020-07-28 3:34 ` Sagi Grimberg
2020-07-28 3:51 ` Chao Leng
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