From: Ming Lei <ming.lei@redhat.com>
To: Chao Leng <lengchao@huawei.com>
Cc: linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
kbusch@kernel.org, axboe@fb.com, hch@lst.de, sagi@grimberg.me
Subject: Re: [PATCH v2 0/3] reduce quiesce time for lots of name spaces
Date: Fri, 7 Aug 2020 21:49:32 +0800 [thread overview]
Message-ID: <20200807134932.GA2122627@T590> (raw)
In-Reply-To: <20200807090559.29582-1-lengchao@huawei.com>
On Fri, Aug 07, 2020 at 05:05:59PM +0800, Chao Leng wrote:
> nvme_stop_queues quiesce queues for all name spaces, now quiesce one by
> one, if there is lots of name spaces, sync wait long time(more than 10s).
> Multipath can not fail over to retry quickly, cause io pause long time.
> This is not expected.
> To reduce quiesce time, we introduce async mechanism for sync SRCUs
> and quiesce queue.
>
Frankly speaking, I prefer to replace SRCU with percpu_refcount:
- percpu_refcount has much less memory footprint than SRCU, so we can simply
move percpu_refcount into request_queue, instead of adding more bytes
into each hctx by this patch
- percpu_ref_get()/percpu_ref_put() isn't slower than srcu_read_lock()/srcu_read_unlock().
- with percpu_refcount, we can remove 'srcu_idx' from hctx_lock/hctx_unlock()
Thanks,
Ming
next prev parent reply other threads:[~2020-08-07 13:49 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-07 9:05 [PATCH v2 0/3] reduce quiesce time for lots of name spaces Chao Leng
2020-08-07 13:49 ` Ming Lei [this message]
2020-08-07 16:37 ` Sagi Grimberg
2020-08-10 2:17 ` Chao Leng
2020-08-10 3:15 ` Ming Lei
2020-08-11 3:13 ` Chao Leng
2020-08-11 20:53 ` Sagi Grimberg
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