From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Wilson Subject: Re: [PATCH] Revert "drm/i915: Kill GTT mappings when moving from GTT domain" Date: Wed, 15 Jun 2011 10:39:06 +0100 Message-ID: References: <1308094989-3153-1-git-send-email-eric@anholt.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by gabe.freedesktop.org (Postfix) with ESMTP id 749AA9E7A6 for ; Wed, 15 Jun 2011 02:39:09 -0700 (PDT) In-Reply-To: <1308094989-3153-1-git-send-email-eric@anholt.net> 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: Eric Anholt , intel-gfx@lists.freedesktop.org List-Id: intel-gfx@lists.freedesktop.org On Tue, 14 Jun 2011 16:43:09 -0700, Eric Anholt wrote: > This reverts commit 4a684a4117abd756291969336af454e8a958802f. > Userland has always been required to set the object's domain to GTT > before using it through a GTT mapping, it's not something that the > kernel is supposed to enforce. (The pagefault support is so that we > can handle multiple mappings without userland having to pin across > them, not so that userland can use GTT after GPU domains without > telling the kernel). The only place that can do accurate per-page tracking of domains is the kernel. (And avoid clflushes for GTT eviction. Ok, so we're not quite there yet.) Relying on userspace to get it right, and for co-operating processes to coordinate their access to buffers is a misfeature. > Fixes 19.2% +/- 0.8% (n=6) performance regression in cairo-gl > firefox-talos-gfx on my T420 latop. Since GTT mappings are fundamentally slow, don't you think this suggests that mesa is doing something wrong? Or a bug in cairo-gl to make mesa act this way? For the record, on my SugarBay, this patch on top of drm-intel-fixes and mesa.git + your instruction streaming, regresses cairo-xlib 4.5s to 4.7s (4%, with a claim of .1% stddev) and improves cairo-gl from 21.5s to 20.1s (6.5%, with a claim of .5% stddev) for the firefox-talos-gfx. [This is a system that can do under 2s for cairo-xlib using vmap and the perf patches I posted before.] -Chris -- Chris Wilson, Intel Open Source Technology Centre