From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: multipart/mixed; boundary="===============8276752086557672799==" MIME-Version: 1.0 From: Sreeni (Sreenivasa) Busam (Stellus) Subject: [SPDK] Regarding NVMe driver command queue depth. Date: Thu, 16 Nov 2017 19:25:42 +0000 Message-ID: <67acc8057cd24c0f8d67926f9f39967d@stellus.com> In-Reply-To: CGME20171116192543uscas1p133a58cadd1606d31d0e8d40e151860c4@uscas1p1.samsung.com List-ID: To: spdk@lists.01.org --===============8276752086557672799== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Hi Paul, I was reading about the driver from SPDK site, and interested in understand= ing the queue depth for a device. "The specification allows for thousands, but most devices support between 3= 2 and 128. The specification makes no guarantees about the performance avai= lable from each queue pair, but in practice the full performance of a devic= e is almost always achievable using just one queue pair. For example, if a = device claims to be capable of 450,000 I/O per second at queue depth 128, i= n practice it does not matter if the driver is using 4 queue pairs each wit= h queue depth 32, or a single queue pair with queue depth 128" When queue depth is mentioned for device, is it the number of commands that= can be issued from application to controller, and outstanding at any time? Is there NVMe driver API to set the queue depth? Is my understanding correc= t if I think that the size of queue is at firmware level? Please give some detail about the parameter. 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