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[62.219.42.90]) by smtp.gmail.com with ESMTPSA id c11-v6sm33015704wri.49.2018.06.06.02.32.22 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 06 Jun 2018 02:32:23 -0700 (PDT) Subject: Re: [PATCH 0/3] Provide more fine grained control over multipathing To: Christoph Hellwig , Roland Dreier Cc: Mike Snitzer , Johannes Thumshirn , Keith Busch , Hannes Reinecke , Laurence Oberman , Ewan Milne , James Smart , Linux Kernel Mailinglist , Linux NVMe Mailinglist , "Martin K . Petersen" , Martin George , John Meneghini References: <20180525125322.15398-1-jthumshirn@suse.de> <20180525130535.GA24239@lst.de> <20180525135813.GB9591@redhat.com> <20180605044222.GA29384@lst.de> From: Sagi Grimberg Message-ID: <4203e888-df87-efd6-f61a-24b43fb710e2@grimberg.me> Date: Wed, 6 Jun 2018 12:32:21 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180605044222.GA29384@lst.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >> We plan to implement all the fancy NVMe standards like ANA, but it >> seems that there is still a requirement to let the host side choose >> policies about how to use paths (round-robin vs least queue depth for >> example). Even in the modern SCSI world with VPD pages and ALUA, >> there are still knobs that are needed. Maybe NVMe will be different >> and we can find defaults that work in all cases but I have to admit >> I'm skeptical... > > The sensible thing to do in nvme is to use different paths for > different queues. Huh? different paths == different controllers so this sentence can't be right... you mean that a path selector will select a controller based on the home node of the local rdma device connecting to it and the running cpu right?