From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Widawsky Subject: Re: [PATCH 3/6] drm/i915: Support write only mappings Date: Tue, 20 Sep 2011 05:37:45 +0000 Message-ID: <20110920053745.GA11743@cloud01> References: <1316492706-31081-1-git-send-email-ben@bwidawsk.net> <1316492706-31081-4-git-send-email-ben@bwidawsk.net> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============0137197283==" Return-path: Received: from cloud01.chad-versace.us (184-106-247-128.static.cloud-ips.com [184.106.247.128]) by gabe.freedesktop.org (Postfix) with ESMTP id E7C11A0223 for ; Mon, 19 Sep 2011 22:34:18 -0700 (PDT) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org To: Keith Packard Cc: Daniel Vetter , intel-gfx@lists.freedesktop.org List-Id: intel-gfx@lists.freedesktop.org --===============0137197283== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="9amGYk9869ThD9tj" Content-Disposition: inline --9amGYk9869ThD9tj Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Sep 19, 2011 at 10:29:15PM -0700, Keith Packard wrote: > On Mon, 19 Sep 2011 21:25:03 -0700, Ben Widawsky wrote: > > When doing a GTT mapping, the pages are not backed until taking a fault. > > If we know that the object is write only, when the fault happens we do = not need > > to make the pages coherent with the CPU. This allows for semi fast pre= faults > > to occur in libdrm at map time. >=20 > Every time I see this stuff, I get confused by the term > 'write-only'. Reading through the code, I remind myself that what you're > actually promising is that any CPU accesses to the object will not > overlap any potential writes by the GPU. The CPU could be reading or > writing, it really doesn't matter. I think of it as, we (libdrm + kernel) promise that the buffer is not guaranteed to be coherent with the GPU. Mesa/client is who should be making the promise to not write to a part of the buffer that the GPU may be accessing. >=20 > Really what you want is a kernel call that does everything except block > on the GPU, right? Yes, exactly. Ben --9amGYk9869ThD9tj Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iQEcBAEBAgAGBQJOeCapAAoJEL9nTIiJEj0pH2AH/3ELksCQrw3wijEyW4HqrNNN n0dZ0+ngppoV1WglAPBbRRpjoqau1cTFs7JD6f2xJM19/BsXhDyg9wLs6NOUkK88 HAnUzhGCgP6F58FcrgsCpITr0ZMM4GPtv7Aagqw2XFwY8E4oQHBlMYKpp5DZrZjT FzmUbQzihsIOnzZosp9pfVYs6RWCwKFTxxRjMB3z2PtAdz7JzHGiC5FXnddtiSOo s0ixU30p4NwZNGgML1xQpBUv8g8muSFIYaopD1YJnv4+F7iIZ77YZVojH57FWlss Jp4z1KXMt0JmwplaxyRmvzHOe6ehSh0Jx4LaxHQCVjVEu42Y5wfJhwny2w9Yq18= =x0o8 -----END PGP SIGNATURE----- --9amGYk9869ThD9tj-- --===============0137197283== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx --===============0137197283==--