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From: Ming Lei <ming.lei@redhat.com>
To: Keith Busch <kbusch@kernel.org>
Cc: Sagi Grimberg <sagi@grimberg.me>, Long Li <longli@microsoft.com>,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
	Jens Axboe <axboe@fb.com>, Hannes Reinecke <hare@suse.de>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 2/2] nvme-pci: poll IO after batch submission for multi-mapping queue
Date: Wed, 13 Nov 2019 11:57:48 +0800
Message-ID: <20191113035748.GD28701@ming.t460p> (raw)
In-Reply-To: <20191113031702.GA25906@redsun51.ssa.fujisawa.hgst.com>

On Wed, Nov 13, 2019 at 12:17:02PM +0900, Keith Busch wrote:
> On Wed, Nov 13, 2019 at 11:05:20AM +0800, Ming Lei wrote:
> > Threaded irq can't help Azure's performance, because Azure's nvme implementation
> > applies aggressive interrupt coalescing.
> 
> This sounds like QD1 latency is really awful if it's coalescing this way.
> 
> Let me restate to ensure I understand how this patch addresses the
> high-depth case: by polling during submission, a multi-threaded high
> depth workload gets to carve up the number of CQEs handled by spreading
> across more CPUs. Real hardware should see fewer completions per
> interrupt,

Right, cause submission's frequency is high enough.

> but we should be able to recreate this issue by enabling
> interrupt coalescing on a real NVMe.

Yeah, I just tried it, and similar intx/s and throughput can be re-created
on one real NVMe.


Thanks,
Ming


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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
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 [this message]
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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