linux-kernel - Re: [Intel-gfx] [PATCH 01/20] drm/atomic: Fix remaining places where !funcs->best

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Message-ID: <20160602224004.GA1819@nuc-i3427.alporthouse.com>
Date:	Thu, 2 Jun 2016 23:40:04 +0100
From:	Chris Wilson <chris@...is-wilson.co.uk>
To:	Daniel Vetter <daniel@...ll.ch>
Cc:	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Heiko Stuebner <heiko@...ech.de>,
	David Airlie <airlied@...ux.ie>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	"open list:VIRTIO CORE, NET..." 
	<virtualization@...ts.linux-foundation.org>,
	Thierry Re ding <thierry.reding@...il.com>,
	Gerd Hoffmann <kraxel@...hat.com>,
	Benjamin Gaignard <benjamin.gaignard@...aro.org>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	Joonyoung Shim <jy0922.shim@...sung.com>,
	Alexey Brodkin <abrodkin@...opsys.com>,
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	Stephen Warren <swarren@...dotorg.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	intel-gfx <intel-gfx@...ts.freedesktop.org>,
	Inki Dae <inki.dae@...sung.com>,
	linux-mediatek@...ts.infradead.org, Stefan Agner <stefan@...er.ch>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Vincent Abriou <vincent.abriou@...com>,
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	Seung-Woo Kim <sw0312.kim@...sung.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"open list:DRM DRIVERS FOR RENESAS" 
	<linux-renesas-soc@...r.kernel.org>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	freedreno@...ts.freedesktop.org,
	Alexandre Courbot <gnurou@...il.com>
Subject: Re: [Intel-gfx] [PATCH 01/20] drm/atomic: Fix remaining places where
 !funcs->best_encoder is valid

On Thu, Jun 02, 2016 at 11:57:02PM +0200, Daniel Vetter wrote:
> drm_encoder_find is an idr lookup. That should be plenty fast,
> especially for modeset code. Usually what's too expensive even for
> modeset code is linear list walks. But Chris just submitted patches to
> convert most of them into simple lookups.

For the idr_find, I'm tempted to replace the mutex with a rwlock. It
helps pathological cases, but in reality there are more crucial
locks around the hw that limit concurrency. ;-)
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre