From mboxrd@z Thu Jan 1 00:00:00 1970 From: Randall Huang Subject: Re: [PATCH] scsi: associate bio write hint with WRITE CDB Date: Fri, 4 Jan 2019 13:22:51 +0800 Message-ID: <20190104052251.GA205256@google.com> References: <20181226041504.66283-1-huangrandall@google.com> <20190103075133.GA5141@infradead.org> <20190103094755.GA96532@google.com> <6152b478ea77dacf57eef6f758ba795f756cd3da.camel@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: "Martin K. Petersen" Cc: jejb@linux.vnet.ibm.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, huangrandall@google.com List-Id: linux-scsi@vger.kernel.org On Thu, Jan 03, 2019 at 11:57:38PM -0500, Martin K. Petersen wrote: > > Ewan, > > > SBC-5 says that support for the grouping function is indicated by the > > GROUP_SUP bit in the Extended Inquiry VPD page (86h). I'm not sure > > how many devices actually support that page though. Probably most > > don't. > > Several devices support it, albeit for various different purposes. It's > one of these wonderful features whose interpretation was left outside > the scope of the spec for a long time. > > So even though we absolutely and positively need to make setting GROUP > NUMBER conditional on GROUP_SUP being reported, we also need additional > information from the storage about how the field should be interpreted. > > The official way to report hinting is for the device to implement the IO > Advice Hints Grouping mode page. I wrote some code to support that but > no vendors that I know of ended up actually shipping an implementation. > A few implemented my older I/O class proposal but didn't ship that > either despite really convincing performance results. > > If Randall has access to a device which implements hinting, I'd love to > know more. I am working on Android phone. The idea is to enable write hint for Turbo write UFS feature. Turbo write feature in UFS 3.x is under discussion in JEDEC JC-64. This patch is the under-lying framework for supporting this feature. > > -- > Martin K. Petersen Oracle Linux Engineering