From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH V2] powerpc/infiniband: Use cache inhibitted and guarded mapping on powerpc Date: Fri, 22 Apr 2016 10:09:27 -0600 Message-ID: <20160422160927.GB12897@obsidianresearch.com> References: <1461139097-10213-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1461278876.3135.18.camel@kernel.crashing.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1461278876.3135.18.camel-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Benjamin Herrenschmidt Cc: "Aneesh Kumar K.V" , paulus-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org, mpe-Gsx/Oe8HsFggBc27wqDAHg@public.gmane.org, linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, Mike Marciniszyn , Doug Ledford , Sean Hefty , Hal Rosenstock , linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org On Fri, Apr 22, 2016 at 08:47:56AM +1000, Benjamin Herrenschmidt wrote: > On Wed, 2016-04-20 at 03:58 -0400, Aneesh Kumar K.V wrote: > > The driver was requesting for a writethrough mapping. But with thoses > > flags we will end up with a SAO mapping because we now have memory > > conherence always enabled. ie, the existing mapping will end up with > > a WIMG value 0b1110 which is Strong Access Order. > > > > Update this to use cache inhibitted guarded mapping > > Why guarded ? If it's performance sensitive (and the driver has > appropriate barriers where needed), you will get write combining > without guarded, you won't with it. This driver uses uncached write combining on x86 Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html