Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756529AbZJVPez (ORCPT ); Thu, 22 Oct 2009 11:34:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756261AbZJVPey (ORCPT ); Thu, 22 Oct 2009 11:34:54 -0400 Received: from 71-20-254-182.war.clearwire-wmx.net ([71.20.254.182]:42735 "EHLO kingsolver.anholt.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756025AbZJVPey (ORCPT ); Thu, 22 Oct 2009 11:34:54 -0400 Subject: Re: [RFC Patch] use MTRR for write combining if PAT is not available From: Eric Anholt To: Suresh Siddha Cc: Thomas Schlichter , Ingo Molnar , Jan Beulich , Jeremy Fitzhardinge , Robert Hancock , Henrique de Moraes Holschuh , "Pallipadi, Venkatesh" , Tejun Heo , "x86@kernel.org" , Yinghai Lu , Thomas Gleixner , Arjan van de Ven , "dri-devel@lists.sourceforge.net" , Ingo Molnar , "linux-kernel@vger.kernel.org" , "jbarnes@virtuousgeek.org" , Thomas Hellstrom , "H. Peter Anvin" In-Reply-To: <1256205210.2530.28.camel@sbs-t61> References: <1394846127@web.de> <4ADF32A0020000780001B20A@vpn.id2.novell.com> <20091021173514.GA32227@elte.hu> <200910212201.36578.thomas.schlichter@web.de> <1256205210.2530.28.camel@sbs-t61> Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-X26ivNY//v0fMy8AGKzp" Date: Thu, 22 Oct 2009 08:34:49 -0700 Message-Id: <1256225689.32075.6.camel@gaiman.anholt.net> Mime-Version: 1.0 X-Mailer: Evolution 2.28.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1879 Lines: 57 --=-X26ivNY//v0fMy8AGKzp Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2009-10-22 at 02:53 -0700, Suresh Siddha wrote: > On Wed, 2009-10-21 at 13:01 -0700, Thomas Schlichter wrote: > > OK, so I think the attached patches should do it. Hopefully I have addr= essed=20 > > all your comments. >=20 > Thomas, >=20 > I have couple of issues with this patchset still. pci_mmap_page_range() > doesn't get called for each fork(). So, we won't be ref counting the > mtrr usage properly. >=20 > I need to think a bit more carefully on this. Can I get back to you > early next week on this, as I am traveling and need to think through > this? >=20 > We already keep track of some of the PAT ref counting using > track_pfn_vma_copy(). And we need to extend/use something similar here. >=20 > Even if we need to extend sysfs or pci vma ops, we need to increment and > decrement the ref count of the mtrr register that gets used. There is no > need to go through num_var_ranges etc. Can we just not create the _wc sysfs entry if we don't have PAT? I don't think there's userland relying on its presence as opposed to the non-_wc entry. --=20 Eric Anholt eric@anholt.net eric.anholt@intel.com --=-X26ivNY//v0fMy8AGKzp Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iEYEABECAAYFAkrge5kACgkQHUdvYGzw6vc/hACeOrqru1n8dzPJotQbH/+SrRhw H3IAnArtWqj9O8zCg1NXr0goyk70eJuJ =QFgQ -----END PGP SIGNATURE----- --=-X26ivNY//v0fMy8AGKzp-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/