From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [PATCH 3/3] drm/i915: Tweak RPS thresholds to more aggressively downclock Date: Thu, 3 Oct 2013 09:41:35 +0200 Message-ID: <20131003074135.GE31334@phenom.ffwll.local> References: <1380126897-21730-1-git-send-email-chris@chris-wilson.co.uk> <1380126897-21730-3-git-send-email-chris@chris-wilson.co.uk> <20131001150401.39daf403@jbarnes-t420> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Received: from mail-ea0-f179.google.com (mail-ea0-f179.google.com [209.85.215.179]) by gabe.freedesktop.org (Postfix) with ESMTP id 65FAFE5F1A for ; Thu, 3 Oct 2013 00:41:18 -0700 (PDT) Received: by mail-ea0-f179.google.com with SMTP id b10so899895eae.10 for ; Thu, 03 Oct 2013 00:41:17 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20131001150401.39daf403@jbarnes-t420> 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: Jesse Barnes Cc: Owen Taylor , intel-gfx@lists.freedesktop.org, "Zhuang, Lena" , =?iso-8859-1?Q?St=E9phane?= Marchesin List-Id: intel-gfx@lists.freedesktop.org On Tue, Oct 01, 2013 at 03:04:01PM -0700, Jesse Barnes wrote: > On Wed, 25 Sep 2013 17:34:57 +0100 > Chris Wilson wrote: > = > > After applying wait-boost we often find ourselves stuck at higher clocks > > than required. The current threshold value requires the GPU to be > > continuously and completely idle for 313ms before it is dropped by one > > bin. Conversely, we require the GPU to be busy for an average of 90% ov= er > > a 84ms period before we upclock. So the current thresholds almost never > > downclock the GPU, and respond very slowly to sudden demands for more > > power. It is easy to observe that we currently lock into the wrong bin > > and both underperform in benchmarks and consume more power than optimal > > (just by repeating the task and measuring the different results). > > = > > An alternative approach, as discussed in the bspec, is to use a > > continuous threshold for upclocking, and an average value for downclock= ing. > > This is good for quickly detecting and reacting to state changes within= a > > frame, however it fails with the common throttling method of waiting > > upon the outstanding frame - at least it is difficult to choose a > > threshold that works well at 15,000fps and at 60fps. So continue to use > > average busy/idle loads to determine frequency change. > > = > > v2: Use 3 power zones to keep frequencies low in steady-state mostly > > idle (e.g. scrolling, interactive 2D drawing), and frequencies high > > for demanding games. In between those end-states, we use a > > fast-reclocking algorithm to converge more quickly on the desired bin. > > = > > v3: Bug fixes - make sure we reset adj after switching power zones. > > = > > v4: Tune - drop the continuous busy thresholds as it prevents us from > > choosing the right frequency for glxgears style swap benchmarks. Instead > > the goal is to be able to find the right clocks irrespective of the > > wait-boost. > > = > > Signed-off-by: Chris Wilson > > Cc: Kenneth Graunke > > Cc: St=E9phane Marchesin > > Cc: Owen Taylor > > Cc: "Meng, Mengmeng" > > Cc: "Zhuang, Lena" > > --- > = > It's a little scary to mess with these, but we've gotten some good > numbers so far so I guess it's ok. > = > As a follow up, it might be nice to expose the power, balanced, > performance profiles to userspace via sysfs. Since we can't solve this > problem for all users and all needs, we can just punt it out to > userspace. :) > = > Reviewed-by: Jesse Barnes All three merged, thanks for patches&review. I've frobbed the first two with tiny style bikesheds: - Dropped the typedef usage for the plain struct drm_i915_private in new code. - Dropped the extern qualifier for the function prototypes in header files. Cheers, Daniel -- = Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch