From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Nicholas A. Bellinger" Subject: Re: [PATCH 3/3] tcm ibmvscsis driver Date: Mon, 21 Mar 2011 16:13:07 -0700 Message-ID: <1300749187.21880.109.camel@haakon2.linux-iscsi.org> References: <20110321100909E.fujita.tomonori@lab.ntt.co.jp> <4D87CF99.7040008@linux.vnet.ibm.com> <1300746873.21880.81.camel@haakon2.linux-iscsi.org> <20110322080628V.fujita.tomonori@lab.ntt.co.jp> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from mail.linux-iscsi.org ([67.23.28.174]:55975 "EHLO linux-iscsi.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932108Ab1CUXUT (ORCPT ); Mon, 21 Mar 2011 19:20:19 -0400 In-Reply-To: <20110322080628V.fujita.tomonori@lab.ntt.co.jp> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: FUJITA Tomonori Cc: brking@linux.vnet.ibm.com, James.Bottomley@suse.de, linux-scsi@vger.kernel.org On Tue, 2011-03-22 at 08:06 +0900, FUJITA Tomonori wrote: > On Mon, 21 Mar 2011 15:34:33 -0700 > "Nicholas A. Bellinger" wrote: > > > On Mon, 2011-03-21 at 17:22 -0500, Brian King wrote: > > > Tomo, > > > > > > Thanks for all the work you've done with this driver. It is much appreciated. > > > > > > What sort of performance are you seeing with this? With filebacked devices, I > > > was seeing around 1 MB/sec doing a basic disktest run. I haven't compared this > > > to ibmvstgt, but I'm pretty sure we did a fair bit better there. Perhaps I've got > > > some setup issue? > > > > > > I tried a ramdisk device and saw this on the server: > > > > > > > > > DMA_TO_DEVICE not supported for RAMDISK_DR with task_sg_chaining=1 > > > > > > > > > > So for the RAMDISK_DR (direct) SGL memory mapping case we do not support > > WRITEs for HW fabric modules using task_sg_changing=1. > > > > Please go ahead and use RAMDISK_MCP instead, and I will look at adding a > > special case in target_core_fabric_configfs.c code to disallow > > RAMDISK_DR symlink creation of configfs ports for target fabric modules > > using task_sg_chaining=1. > > I really want to remove 'task_sg_chaining=0', all the drivers support > sg chaining. It's a hacky. What drivers doesn't support it? It's only drivers for which we are not using HW provided scatterlists into TCM backend memory, which today is just iscsi_target_mod iscsi_target_rx_thread() -> sock_recvmsg() code. So that said, dropping TFO->task_sg_chaning is fine with me. It will still be useful for TCM to determine this for a fabric module using a new flag (for the current stable iscsi_target_mod code case) so that non iscsi_target_mod of RAMDISK_DR Port/LUN export can be -ENOSYS within target_core_fabric_configfs.c:target_fabric_port_link(). --nab