From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [PATCH 1/3] drm/i915: swizzling support for snb/ivb Date: Wed, 1 Feb 2012 23:16:19 +0100 Message-ID: <20120201221619.GC8395@phenom.ffwll.local> References: <1328024876-5240-1-git-send-email-daniel.vetter@ffwll.ch> <4F29B012.4060905@bwidawsk.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-wi0-f177.google.com (mail-wi0-f177.google.com [209.85.212.177]) by gabe.freedesktop.org (Postfix) with ESMTP id DFE2EA0CF5 for ; Wed, 1 Feb 2012 14:16:16 -0800 (PST) Received: by wico1 with SMTP id o1so1591395wic.36 for ; Wed, 01 Feb 2012 14:16:15 -0800 (PST) Content-Disposition: inline In-Reply-To: <4F29B012.4060905@bwidawsk.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: Ben Widawsky Cc: Daniel Vetter , Intel Graphics Development List-Id: intel-gfx@lists.freedesktop.org On Wed, Feb 01, 2012 at 01:35:14PM -0800, Ben Widawsky wrote: > On 01/31/2012 07:47 AM, Daniel Vetter wrote: > > We have to do this manually. Somebody had a Great Idea. > > > > I've measured speed-ups just a few percent above the noise level > > (below 5% for the best case), but no slowdows. Chris Wilson measured > > quite a bit more (10-20% above the usual snb variance) on a more > > recent and better tuned version of sna, but also recorded a few > > slow-downs on benchmarks know for uglier amounts of snb-induced > > variance. > > > > v2: Incorporate Ben Widawsky's preliminary review comments and > > elaborate a bit about the performance impact in the changelog. > > > > Acked-by: Chris Wilson > > Signed-Off-by: Daniel Vetter > > You didn't address one questions I really cared about, how is it safe to > ignore channel 3 size? While I'm at it, I wonder what is in these > registers if you have less than 256MB. If the answer is zero, then your > check isn't safe enough below. Hm, I've thought I've answered that in the mail to your review: 3 channel ddr configurations only exists on i7 chips without a gpu attached. Furthermore swizzling is only sensible when we have 2 channels anyway. For the other issue, I suspect 256mb is simply the smallest dimm you can buy for ddr3 - I don't have the spec for that though, but the smallest dimm my local supplier sells is 512mb, anyway ;-) > As an aside, this will potentially break our simulation environment, but > that's environment fail. I think we can quirk that by detecting has or something like that ... Cheers, Daniel -- Daniel Vetter Mail: daniel@ffwll.ch Mobile: +41 (0)79 365 57 48