From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [PATCH] drm/i915: use hsw rps tuning values everywhere on gen6+ Date: Mon, 20 Aug 2012 20:44:16 +0200 Message-ID: <20120820184416.GD5170@phenom.ffwll.local> References: <1345020105-5933-1-git-send-email-daniel.vetter@ffwll.ch> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-we0-f177.google.com (mail-we0-f177.google.com [74.125.82.177]) by gabe.freedesktop.org (Postfix) with ESMTP id 2914A9E89F for ; Mon, 20 Aug 2012 11:43:54 -0700 (PDT) Received: by weyr3 with SMTP id r3so4456568wey.36 for ; Mon, 20 Aug 2012 11:43:53 -0700 (PDT) Content-Disposition: inline In-Reply-To: <1345020105-5933-1-git-send-email-daniel.vetter@ffwll.ch> 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: Intel Graphics Development Cc: Daniel Vetter , stable@vger.kernel.org List-Id: intel-gfx@lists.freedesktop.org On Wed, Aug 15, 2012 at 10:41:45AM +0200, Daniel Vetter wrote: > James Bottomley reported [1] a massive power regression, due to the > enabling of semaphores by default in 3.5. A workaround for him is to > again disable semaphores. And indeed, his system has a very hard time > to entre rc6 with semaphores enabled. > > Ben Widawsky run around with a kill-a-watt a lot and noticed: > - There are indeed a few rare systems that seem to have a hard time > entering rc6 when desktop-idle. > - One machine, The Indestructible Toshiba regressed in this behaviour > between 3.5 and 3.6 in a merge commit! So rc6 behaviour with the > current setting seems to be highly timing dependent and not robust > at all. > - The behaviour James reported wrt semaphores seems to be a freak > timing thing that only happens on his specific machine, confirming > that enabling semaphores shouldn't reduce rc6 residency. > > Now furthermore the Google ChromeOS guys reported [2] a while ago that > at least on some machines a simply a blinking cursor can keep the gpu > turbo at the highest frequency. This is because the current rps limits > used on snb/ivb are highly asymmetric. > > On the theory that gpu turbo and rc6 tuning values are related, we've > tried whether the much saner looking (since much less asymmetric) rps > tuning values used for hsw would also help entering rc6 more robustly. > > And it seems to work. > > Reference[1]: http://lists.freedesktop.org/archives/dri-devel/2012-July/025675.html > Reference[2]: http://lists.freedesktop.org/archives/intel-gfx/2012-July/018692.html > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=53393 > Tested-by: Ben Widawsky > Cc: stable@vger.kernel.org > Signed-off-by: Daniel Vetter Ok, I've merged this one here, making the commit message a bit more cautious. Unfortnately we don't seem to have the understanding (nor the resources to gain it) of the hw to do better than copy&paste what we get from the hw team :( -Daniel -- Daniel Vetter Mail: daniel@ffwll.ch Mobile: +41 (0)79 365 57 48