Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753627AbZCZEMi (ORCPT ); Thu, 26 Mar 2009 00:12:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750925AbZCZEM2 (ORCPT ); Thu, 26 Mar 2009 00:12:28 -0400 Received: from home.keithp.com ([63.227.221.253]:56501 "EHLO keithp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750824AbZCZEM2 (ORCPT ); Thu, 26 Mar 2009 00:12:28 -0400 X-Greylist: delayed 530 seconds by postgrey-1.27 at vger.kernel.org; Thu, 26 Mar 2009 00:12:27 EDT Subject: Re: [PATCH 4/6] drm/i915: Fix lock order reversal in shmem pread path. From: Keith Packard To: Dave Airlie Cc: keithp@keithp.com, Eric Anholt , dri-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org In-Reply-To: References: <1238017510-26784-1-git-send-email-eric@anholt.net> <1238017510-26784-2-git-send-email-eric@anholt.net> <1238017510-26784-3-git-send-email-eric@anholt.net> <1238017510-26784-4-git-send-email-eric@anholt.net> <1238017510-26784-5-git-send-email-eric@anholt.net> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-NZOtivrmD3fBmnpfQmXa" Date: Wed, 25 Mar 2009 21:03:13 -0700 Message-Id: <1238040193.26771.186.camel@aiko.keithp.com> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1530 Lines: 45 --=-NZOtivrmD3fBmnpfQmXa Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Wed, 2009-03-25 at 23:30 +0000, Dave Airlie wrote: >=20 > I've no idea when a fault is likely in the fast case, i.e. will it happen > usually on the first page etc, because if it happens on the last page and= =20 > you fallback and restart the whole copy, I would think that would be=20 > sub-optimal, granted it could get ugly quick, but this code has already=20 > hit a few branches on the tree. The data in question is presumably 'hot', and so unlikely to be swapped out. Testing the slow paths doing a complete copy is fairly easy, while testing partial copies would be considerably more difficult. The combination of these two seems to encourage a careful and simplistic slow path. We can always make it 'faster' in the future, but having it wrong from the first seems sub-optimal. --=20 keith.packard@intel.com --=-NZOtivrmD3fBmnpfQmXa Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iD8DBQBJyv6BQp8BWwlsTdMRAjokAKDcXwteMwFlxf5eY0whr8+Ta2sa1ACfSDvZ xtUZ4JYVyZnufH2bmtvB/yI= =/NQW -----END PGP SIGNATURE----- --=-NZOtivrmD3fBmnpfQmXa-- -- 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/