From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Martin K. Petersen" Subject: Re: [PATCH V4 0/3] scsi: core: avoid big pre-allocation for sg list Date: Mon, 13 May 2019 22:06:13 -0400 Message-ID: References: <20190428073932.9898-1-ming.lei@redhat.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: <20190428073932.9898-1-ming.lei@redhat.com> (Ming Lei's message of "Sun, 28 Apr 2019 15:39:29 +0800") Sender: netdev-owner@vger.kernel.org To: Ming Lei Cc: James Bottomley , linux-scsi@vger.kernel.org, "Martin K . Petersen" , linux-block@vger.kernel.org, Christoph Hellwig , Bart Van Assche , "Ewan D . Milne" , Hannes Reinecke , Sagi Grimberg , Chuck Lever , netdev@vger.kernel.org, linux-nvme@lists.infradead.org List-Id: linux-scsi@vger.kernel.org Ming, > Since supporting to blk-mq, big pre-allocation for sg list is > introduced, this way is very unfriendly wrt. memory consumption. Applied to 5.3/scsi-queue with some clarifications to the commit descriptions. I am not entirely sold on 1 for the inline protection SGL size. NVMe over PCIe is pretty constrained thanks to the metadata pointer whereas SCSI DIX uses a real SGL for the PI. Consequently, straddling a page is not that uncommon for large, sequential I/Os. But let's try it out. If performance suffers substantially, we may want to bump it to 2. -- Martin K. Petersen Oracle Linux Engineering