From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Evers Subject: Re: [PATCH 0/2] Change type-2 dif to use rq embedded 32 byte cdb Date: Wed, 19 Dec 2012 09:12:58 -0500 Message-ID: <50D1CB6A.6030007@redhat.com> References: <1353528468-5664-1-git-send-email-revers@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mx1.redhat.com ([209.132.183.28]:36817 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752589Ab2LSOOY (ORCPT ); Wed, 19 Dec 2012 09:14:24 -0500 In-Reply-To: <1353528468-5664-1-git-send-email-revers@redhat.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: linux-scsi@vger.kernel.org, chad.dupuis@qlogic.com, giridhar.malavali@qlogic.com, scameron@beardog.cce.hp.com, mike.miller@hp.com, dan.j.williams@intel.com, fushun@marvell.com On 11/21/2012 03:07 PM, Rob Evers wrote: > These patches replace the original t10 type 2 dif mempool implementation > by increasing the block and scsi cdb maximum sizes from 16 to 32 bytes. > The cdb embedded in the request structure can then be used for type 2 > dif commands, or other 32 byte cdbs as required. > > Motivation for this is that type-2 dif commands should be treated as > any other read/writes generally, without any performance penalty. > > This patch set conflicts with a patch previously posted which addresses > a race in UA induced retries with type 2 dif commands. These patches also > address that problem: > > http://marc.info/?l=linux-scsi&m=135186352200668&w=2 > > Testing: > > Readily reproduced the race condition panic by simultaneously > inducing UAs while load testing 8 scsi_debug devices. With patch > applied, same testing ran for 15 hours without a panic. > > Sanity tested performance using scsi_debug, with and without > type 2 dif enabled. Order 80% performance increase noticed > with patches when scsi_debug was running in dif type 2 mode. > Running scsi_debug without type 2 dif, performance was approximately > equal. > > Used 3.7.0-rc5 for testing and patch generation. > > root (2): > Change the cdb size limits in block and scsi to 32 bytes > Change dif type 2 commands to use embedded 32 byte cdb > > drivers/scsi/sd.c | 45 +-------------------------------------------- > drivers/scsi/sd.h | 5 ----- > include/linux/blkdev.h | 2 +- > include/scsi/scsi_cmnd.h | 13 ++----------- > 4 files changed, 4 insertions(+), 61 deletions(-) > James, Can you give some input on this? Thanks, Rob