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Wed, 09 Feb 2022 21:52:47 -0500 X-MC-Unique: e8Q6eWFYOwmjm_19GQyPGA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6E4668144E0; Thu, 10 Feb 2022 02:52:46 +0000 (UTC) Received: from [10.22.32.245] (unknown [10.22.32.245]) by smtp.corp.redhat.com (Postfix) with ESMTP id 835A71002391; Thu, 10 Feb 2022 02:52:45 +0000 (UTC) Message-ID: <56fb153a-ba0e-605b-e774-885c259965a6@redhat.com> Date: Wed, 9 Feb 2022 21:52:45 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH] nvme-multipath: add an 'ana_groups_only' module option To: Christoph Hellwig , Hannes Reinecke Cc: Sagi Grimberg , Keith Busch , linux-nvme@lists.infradead.org References: <20220207100005.34404-1-hare@suse.de> <20220209080747.GA9851@lst.de> From: John Meneghini Organization: RHEL Core Storge Team In-Reply-To: <20220209080747.GA9851@lst.de> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jmeneghi@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220209_185251_830872_6A1088D4 X-CRM114-Status: GOOD ( 23.44 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 2/9/22 03:07, Christoph Hellwig wrote: > On Mon, Feb 07, 2022 at 11:00:05AM +0100, Hannes Reinecke wrote: >> On large installations the ANA log buffer can be exceedingly large; >> we've come across a controller with 49 ANA Group Descriptors and >> 65536 namespaces, resulting in an ANA buffer with an order-7 allocation. >> And this is just to validate that the namespace ID is _really_listed >> in the log page. >> So to avoid an overly large memory allocation we can leverage the >> 'RGO' bit when retrieving the ANA log page, and check whether the >> ANA group ID from the namespace is found in the ANA descriptors. >> That cuts down the memory allocation, and provides the same result. >> But to be on the safe side I've added a module option 'ana_groups_only' >> to switch between modes. > > How is this supposed to work? We'll fail to see what namespaces > the change applies to. > > So in doubt fix the controller config to be less broken (and say hello > to NetApp and explain them they do not need more namespace for more > performance), and if that fails switch to a vmalloc allocation for > the buffer. I agree with Christoph. I don't see the point in supporting 65536 namespaces across 49 ana groups or controllers. The problem here is: the vendor is trying to turn NVMe into SCSI. Moreover, I don't understand how implementing this as a MODULE_PARM is supposed to work. If you configure this module parameter on it assumes all NVMe-oF arrays connected to the host support RGO. What's really needed here is some kind of protocol mechanism that will allow the host to dynamically discovery if RGO is supported on a controller by controller basis. And this isn't an NetApp array. Just look at who's asking for this change if you want a clue as to what NVMe-oF array is asking for this. I know for a fact this isn't a NetApp array. /John