From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: [HMM-CDM 0/5] Cache coherent device memory (CDM) with HMM Date: Thu, 15 Jun 2017 08:07:56 +1000 Message-ID: <1497478076.2897.46.camel@kernel.crashing.org> References: <20170614201144.9306-1-jglisse@redhat.com> <8219f8fb-65bb-7c6b-6c4c-acc0601c1e0f@intel.com> <20170614213800.GD4160@redhat.com> <3a617630-2406-da49-707c-4959a2afd8e1@intel.com> Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <3a617630-2406-da49-707c-4959a2afd8e1@intel.com> Sender: owner-linux-mm@kvack.org List-ID: Content-Type: text/plain; charset="iso-8859-1" To: Dave Hansen , Jerome Glisse Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, John Hubbard , David Nellans , cgroups@vger.kernel.org, Dan Williams , Ross Zwisler , Johannes Weiner , Michal Hocko , Vladimir Davydov , Balbir Singh , Aneesh Kumar , "Paul E . McKenney" On Wed, 2017-06-14 at 14:58 -0700, Dave Hansen wrote: > > > http://www.uefi.org/sites/default/files/resources/ACPI_6_2.pdf > >=20 > > It doesn't interact with that. HMM-CDM is a set of helper that don't > > do anything unless instructed so. So for device memory to be presented > > as HMM-CDM you need to hotplug it as ZONE_DEVICE(DEVICE_PUBLIC) which > > can be done with the helper introduced in patch 2 of this patchset. >=20 > I guess I'm asking whether we *should* instruct HMM-CDM to manage all > coherent device memory.=C2=A0 If not, where do we draw the line for what = we > use HMM-CDM, and for what we use the core MM? Well, if you want the features of HMM ... It basically boils down to whether you have some kind of coherent processing unit close to that memory and want to manage transparent migration of pages between system and device memory, that sort of thing. Cheers, 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