From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keith Packard Subject: Re: [PATCH 1/2] drm/i915: Remove use of the autoreported ringbuffer HEAD position Date: Wed, 08 Feb 2012 11:13:28 -0800 Message-ID: <8639alf89z.fsf@sumi.keithp.com> References: <1328708054-26350-1-git-send-email-chris@chris-wilson.co.uk> <20120208145425.GD5030@phenom.ffwll.local> <867gzxfcrm.fsf@sumi.keithp.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from keithp.com (home.keithp.com [63.227.221.253]) by gabe.freedesktop.org (Postfix) with ESMTP id 8FD669E764 for ; Wed, 8 Feb 2012 11:13:30 -0800 (PST) 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: Daniel Vetter Cc: intel-gfx@lists.freedesktop.org List-Id: intel-gfx@lists.freedesktop.org <#part sign=pgpmime> On Wed, 8 Feb 2012 19:02:47 +0100, Daniel Vetter wrote: > The issue is that the first one introduces a pretty decent perf > regression, iirc Chris mentions something much large than 10x slowdown > on certain cairo traces on sna. So we can only merge the first one > together with the second one. Is there any effect on mesa or uxa? > Yeah, that's kinda the issue which I've failed to phrase clearly in my mail ;-) Frightening patches with that kind of global scope need a reason far more compelling than a performance regression caused by a separate correctness fix. If we need the correctness patch to resolve a known problem (especially a regression), then we'll take the performance hit and fix that in the next release. > Without this issue being confirmed on older machines I'm leaning > towards merging both patches to -next - after all snb never really > regressed because the offending commit changed behaviour from "dies as > soon as the ring wraps" to "sometimes corrupts the ring". If we don't see any significant issues in 'normal' usage (mesa and uxa), then I agree, we should push both patches to -next. -- keith.packard@intel.com