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Tue, 29 Nov 2022 06:33:52 -0800 (PST) Message-ID: <9f45de57-353a-08c9-5d7f-57d7acc67b18@kernel.dk> Date: Tue, 29 Nov 2022 07:33:51 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0 Subject: Re: [PATCH v2 2/2] nvme: support io stats on the mpath device Content-Language: en-US To: Sagi Grimberg , linux-nvme@lists.infradead.org Cc: Christoph Hellwig , Keith Busch , Chaitanya Kulkarni , Hannes Reinecke , linux-block@vger.kernel.org References: <20221003094344.242593-1-sagi@grimberg.me> <20221003094344.242593-3-sagi@grimberg.me> From: Jens Axboe In-Reply-To: <20221003094344.242593-3-sagi@grimberg.me> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221129_063356_150664_017AAD6E X-CRM114-Status: GOOD ( 13.80 ) 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 10/3/22 3:43 AM, Sagi Grimberg wrote: > Our mpath stack device is just a shim that selects a bottom namespace > and submits the bio to it without any fancy splitting. This also means > that we don't clone the bio or have any context to the bio beyond > submission. However it really sucks that we don't see the mpath device > io stats. > > Given that the mpath device can't do that without adding some context > to it, we let the bottom device do it on its behalf (somewhat similar > to the approach taken in nvme_trace_bio_complete). > > When the IO starts, we account the request for multipath IO stats using > REQ_NVME_MPATH_IO_STATS nvme_request flag to avoid queue io stats disable > in the middle of the request. Reviewed-by: Jens Axboe -- Jens Axboe