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([2601:647:4802:9070:104e:47d9:f0fe:a697]) by smtp.gmail.com with ESMTPSA id p188sm1237449pgp.65.2020.10.20.01.22.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 20 Oct 2020 01:22:38 -0700 (PDT) Subject: Re: [PATCH 0/1] nvmet: allow user to set req alloc flag To: Chaitanya Kulkarni , linux-nvme@lists.infradead.org References: <20201020014417.3604-1-chaitanya.kulkarni@wdc.com> From: Sagi Grimberg Message-ID: <74e2bc85-3752-08fe-4f2c-07130ab4411d@grimberg.me> Date: Tue, 20 Oct 2020 01:22:35 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201020014417.3604-1-chaitanya.kulkarni@wdc.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201020_042240_165819_AAC8E794 X-CRM114-Status: GOOD ( 18.95 ) 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: logang@deltatee.com, hch@lst.de Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org > Hi, > > When using NVMeOF target in the passthru mode we allocate the request > with BLK_MQ_REQ_NOWAIT flag. This allocates the request in the following > manner :- > > nvme_alloc_request() > blk_mq_alloc_rquest() > blk_mq_queue_enter() > if (flag & BLK_MQ_REQ_NOWAIT) > return -EBUSY; <-- return if busy. > > On the NVMe controller which I've the fio random write workload running > parallel on 32 namespaces with higher queue depth results in I/O error, > where blk_mq_queue_enter() returning -EBUSY as shown above. This problem > is not easy to reproduce but occurs once in a while with following error > (See 1 for detailed log) :- > > test1: (groupid=0, jobs=32): err= 5 > (file:io_u.c:1744, func=io_u error, error=Input/output error): > > When the flag BLK_MQ_REQ_NOWAIT is removed from the allocation the > workload doen't result in the error. > > This patch fixes the problem with the request allocation by adding > a new configfs attribute so that user can optionally decide whether > to use BLK_MQ_REQ_NOWAIT or not. We retain the default behavior by > using BLK_MQ_REQ_NOWAIT when creating the nvmet passthru subsystem. Why should we ever set REQ_NOWAIT at all? Nothing prevents the host(s) queue depth from exceeding the controller queue depth... _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme