From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Martin K. Petersen" Subject: Re: [PATCH v4 00/14] mpt3sas driver NVMe support: Date: Thu, 31 Aug 2017 23:22:44 -0400 Message-ID: References: <1503322344-5900-1-git-send-email-suganath-prabu.subramani@broadcom.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from aserp1040.oracle.com ([141.146.126.69]:35310 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750868AbdIADXT (ORCPT ); Thu, 31 Aug 2017 23:23:19 -0400 In-Reply-To: (Suganath Prabu Subramani's message of "Thu, 31 Aug 2017 10:28:06 +0530") Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Suganath Prabu Subramani Cc: "Martin K. Petersen" , linux-scsi@vger.kernel.org, Sathya Prakash , Kashyap Desai , linux-kernel@vger.kernel.org, Chaitra Basappa , Sreekanth Reddy , linux-nvme@lists.infradead.org Hi Suganath, > Let me explain - NVME device fast path is possible in two ways. IEEE > SGL and PRP SGL. Due to h/w constraint we choose IEEE SGL only for > smaller IO size. Both above is true h/w Fast Path and no firmware > involvement. > Agree with you. We are planning to see if we can keep only simple Fast > Path using only PRP. That would be great, thank you! > Currently there is no performance issue for UNMAP translation in FW. Good! >> And yet patch 4 circumvents that statement by adding support for >> encapsulated commands to bypass the FW translation... > > This path is not due to performance reason. User wants to interact > with NVME drive in native NVME command for management. Patch 4 states: "This encapsulated NVMe command is used by applications to send direct NVMe commands to NVMe drives or for handling unmap where the translation at controller/firmware level is having performance issues." -- Martin K. Petersen Oracle Linux Engineering