From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qc0-f176.google.com (mail-qc0-f176.google.com [209.85.216.176]) by kanga.kvack.org (Postfix) with ESMTP id 445576B0032 for ; Wed, 22 Apr 2015 22:36:44 -0400 (EDT) Received: by qcbii10 with SMTP id ii10so2714710qcb.2 for ; Wed, 22 Apr 2015 19:36:44 -0700 (PDT) Received: from gate.crashing.org (gate.crashing.org. [63.228.1.57]) by mx.google.com with ESMTPS id f108si521063qga.86.2015.04.22.19.36.43 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Wed, 22 Apr 2015 19:36:43 -0700 (PDT) Message-ID: <1429756592.4915.23.camel@kernel.crashing.org> Subject: Re: Interacting with coherent memory on external devices From: Benjamin Herrenschmidt Date: Thu, 23 Apr 2015 12:36:32 +1000 In-Reply-To: References: <20150421214445.GA29093@linux.vnet.ibm.com> <20150422000538.GB6046@gmail.com> <20150422131832.GU5561@linux.vnet.ibm.com> <20150422170737.GB4062@gmail.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Jerome Glisse , "Paul E. McKenney" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, jglisse@redhat.com, mgorman@suse.de, aarcange@redhat.com, riel@redhat.com, airlied@redhat.com, aneesh.kumar@linux.vnet.ibm.com, Cameron Buschardt , Mark Hairgrove , Geoffrey Gerfin , John McKenna , akpm@linux-foundation.org On Wed, 2015-04-22 at 13:17 -0500, Christoph Lameter wrote: > > > But again let me stress that application that want to be in control will > > stay in control. If you want to make the decission yourself about where > > things should end up then nothing in all we are proposing will preclude > > you from doing that. Please just think about others people application, > > not just yours, they are a lot of others thing in the world and they do > > not want to be as close to the metal as you want to be. We just want to > > accomodate the largest number of use case. > > What I think you want to do is to automatize something that should not be > automatized and cannot be automatized for performance reasons. You don't know that. > Anyone > wanting performance (and that is the prime reason to use a GPU) would > switch this off because the latencies are otherwise not controllable and > those may impact performance severely. There are typically multiple > parallel strands of executing that must execute with similar performance > in order to allow a data exchange at defined intervals. That is no longer > possible if you add variances that come with the "transparency" here. Stop trying to apply your unique usage model to the entire world :-) Ben. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org