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Tue, 12 Nov 2019 22:58:01 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AE4FEDB60; Wed, 13 Nov 2019 03:57:59 +0000 (UTC) Received: from ming.t460p (ovpn-8-28.pek2.redhat.com [10.72.8.28]) by smtp.corp.redhat.com (Postfix) with ESMTPS id EBF1462937; Wed, 13 Nov 2019 03:57:52 +0000 (UTC) Date: Wed, 13 Nov 2019 11:57:48 +0800 From: Ming Lei To: Keith Busch Subject: Re: [PATCH 2/2] nvme-pci: poll IO after batch submission for multi-mapping queue Message-ID: <20191113035748.GD28701@ming.t460p> References: <20191108035508.26395-1-ming.lei@redhat.com> <20191108035508.26395-3-ming.lei@redhat.com> <20191111204446.GA26028@lst.de> <20191112023920.GD15079@ming.t460p> <8198fd99-6b47-7594-ba1c-4a15ffe25269@suse.de> <20191112164947.GB29135@redsun51.ssa.fujisawa.hgst.com> <20191113030520.GC28701@ming.t460p> <20191113031702.GA25906@redsun51.ssa.fujisawa.hgst.com> MIME-Version: 1.0 In-Reply-To: <20191113031702.GA25906@redsun51.ssa.fujisawa.hgst.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-MC-Unique: K8exkAPdP4G10lPeqR2jPg-1 X-Mimecast-Spam-Score: 0 Content-Disposition: inline X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191112_195806_078297_1520E42F X-CRM114-Status: GOOD ( 11.11 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Sagi Grimberg , Long Li , "linux-nvme@lists.infradead.org" , Jens Axboe , Hannes Reinecke , Christoph Hellwig Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org 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 _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme