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From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Sagi Grimberg <sagi@grimberg.me>, Long Li <longli@microsoft.com>,
	linux-nvme@lists.infradead.org, Jens Axboe <axboe@fb.com>,
	Keith Busch <kbusch@kernel.org>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 2/2] nvme-pci: poll IO after batch submission for multi-mapping queue
Date: Mon, 11 Nov 2019 21:44:46 +0100
Message-ID: <20191111204446.GA26028@lst.de> (raw)
In-Reply-To: <20191108035508.26395-3-ming.lei@redhat.com>

On Fri, Nov 08, 2019 at 11:55:08AM +0800, Ming Lei wrote:
> f9dde187fa92("nvme-pci: remove cq check after submission") removes
> cq check after submission, this change actually causes performance
> regression on some NVMe drive in which single nvmeq handles requests
> originated from more than one blk-mq sw queues(call it multi-mapping
> queue).

> Follows test result done on Azure L80sv2 guest with NVMe drive(
> Microsoft Corporation Device b111). This guest has 80 CPUs and 10
> numa nodes, and each NVMe drive supports 8 hw queues.

Have you actually seen this on a real nvme drive as well?

Note that it is kinda silly to limit queues like that in VMs, so I
really don't think we should optimize the driver for this particular
case.

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  reply index

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-08  3:55 [PATCH 0/2] nvme-pci: improve IO performance via poll after batch submission Ming Lei
2019-11-08  3:55 ` [PATCH 1/2] nvme-pci: move sq/cq_poll lock initialization into nvme_init_queue Ming Lei
2019-11-08  4:12   ` Keith Busch
2019-11-08  7:09     ` Ming Lei
2019-11-08  3:55 ` [PATCH 2/2] nvme-pci: poll IO after batch submission for multi-mapping queue Ming Lei
2019-11-11 20:44   ` Christoph Hellwig [this message]
2019-11-12  0:33     ` Long Li
2019-11-12  1:35       ` Sagi Grimberg
2019-11-12  2:39       ` Ming Lei
2019-11-12 16:25         ` Hannes Reinecke
2019-11-12 16:49           ` Keith Busch
2019-11-12 17:29             ` Hannes Reinecke
2019-11-13  3:05               ` Ming Lei
2019-11-13  3:17                 ` Keith Busch
2019-11-13  3:57                   ` Ming Lei
2019-11-12 21:20         ` Long Li
2019-11-12 21:36           ` Keith Busch
2019-11-13  0:50             ` Long Li
2019-11-13  2:24           ` Ming Lei
2019-11-12  2:07     ` Ming Lei
2019-11-12  1:44   ` Sagi Grimberg
2019-11-12  9:56     ` Ming Lei
2019-11-12 17:35       ` Sagi Grimberg
2019-11-12 21:17         ` Long Li
2019-11-12 23:44         ` Jens Axboe
2019-11-13  2:47         ` Ming Lei
2019-11-12 18:11   ` Nadolski, Edmund
2019-11-13 13:46     ` Ming Lei

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