From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keith Busch Subject: Re: [PATCH 4/7] node: Add memory caching attributes Date: Mon, 26 Nov 2018 08:14:47 -0700 Message-ID: <20181126151446.GK26707@localhost.localdomain> References: <20181114224921.12123-2-keith.busch@intel.com> <20181114224921.12123-5-keith.busch@intel.com> <91698cef-cdcd-5143-884f-3da5536e156f@arm.com> <20181119230600.GC26707@localhost.localdomain> <731533d5-26e1-ade7-1a63-d1f85461d091@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <731533d5-26e1-ade7-1a63-d1f85461d091@arm.com> Sender: linux-kernel-owner@vger.kernel.org To: Anshuman Khandual Cc: linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org, Greg Kroah-Hartman , Rafael Wysocki , Dave Hansen , Dan Williams List-Id: linux-acpi@vger.kernel.org On Thu, Nov 22, 2018 at 06:59:21PM +0530, Anshuman Khandual wrote: > > > On 11/20/2018 04:36 AM, Keith Busch wrote: > > On Mon, Nov 19, 2018 at 09:44:00AM +0530, Anshuman Khandual wrote: > >> On 11/15/2018 04:19 AM, Keith Busch wrote: > >>> System memory may have side caches to help improve access speed. While > >>> the system provided cache is transparent to the software accessing > >>> these memory ranges, applications can optimize their own access based > >>> on cache attributes. > >> > >> Cache is not a separate memory attribute. It impacts how the real attributes > >> like bandwidth, latency e.g which are already captured in the previous patch. > >> What is the purpose of adding this as a separate attribute ? Can you explain > >> how this is going to help the user space apart from the hints it has already > >> received with bandwidth, latency etc properties. > > > > I am not sure I understand the question here. Access bandwidth and latency > > are entirely attributes different than what this patch provides. If the > > system side-caches memory, the associativity, line size, and total size > > can optionally be used by software to improve performance. > > Okay but then does this belong to this series which about memory attributes ? This patch series is about exporting memory attributes, and this system memory caching is one such attribute, so yes, I think it belongs.