From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932478AbXCRRZI (ORCPT ); Sun, 18 Mar 2007 13:25:08 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752676AbXCRRZH (ORCPT ); Sun, 18 Mar 2007 13:25:07 -0400 Received: from rwcrmhc12.comcast.net ([216.148.227.152]:52684 "EHLO rwcrmhc12.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752671AbXCRRZE (ORCPT ); Sun, 18 Mar 2007 13:25:04 -0400 X-Greylist: delayed 301 seconds by postgrey-1.27 at vger.kernel.org; Sun, 18 Mar 2007 13:25:04 EDT Subject: Re: [linux-pm] [2/6] 2.6.21-rc2: known regressions From: Jim Gettys Reply-To: jg@laptop.org To: Ingo Molnar Cc: Pavel Machek , Ash Milsted , dmitry.torokhov@gmail.com, Arkadiusz Miskiewicz , linux-pm@lists.osdl.org, Jens Axboe , linux-input@atrey.karlin.mff.cuni.cz, Alexey Starikovskiy , linux-usb-devel@lists.sourceforge.net, Jeff Chua , Meelis Roos , Janosch Machowinski , Linux Kernel Mailing List , Adrian Bunk , linux-acpi@vger.kernel.org, "Eric W. Biederman" , Thomas Meyer , "Michael S. Tsirkin" , Andrew Morton , Linus Torvalds In-Reply-To: <20070318160707.GC12673@elte.hu> References: <20070305015034.GG3441@stusta.de> <20070308123143.GF5149@mellanox.co.il> <20070308192554.GA2999@elte.hu> <20070308230705.GA4611@elte.hu> <20070309111957.GA3928@elf.ucw.cz> <20070318160707.GC12673@elte.hu> Content-Type: text/plain Organization: OLPC Date: Sun, 18 Mar 2007 12:40:45 -0400 Message-Id: <1174236045.6832.9.camel@localhost> Mime-Version: 1.0 X-Mailer: Evolution 2.8.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2007-03-18 at 17:07 +0100, Ingo Molnar wrote: > * Pavel Machek wrote: > > > > Some day we may have modesetting support in the kernel for some > > > graphics hw, right now it's pretty damn spotty. > > > > Yep, that's the way to go. > > hey, i wildly supported this approach ever since 1996, when GGI came up > :-/ > So wildly you wrote tons of code.... ;-). More seriously, at the time, XFree86 would have spat in your face for any such thing. Thankfully, times are changing. Also more seriously, a somewhat hybrid approach is in order for mode setting: simple mode setting isn't much code and is required for sane behavior on crash (it is nice to get oopses onto a screen); but the full blown mode setting/configuration problem is so large that on some hardware, it is likely left best left to a helper process (not the X server). Also key to get sane behavior out of the scheduler is to get the X server to yield (sleep in the kernel) rather than busy waiting when the GPU is busy; a standardized interface for this for both fbdev and dri is in order. Right now, X is a misbehaving compute bound process rather than the properly interactive process it can/should/will be, releasing the CPU whenever the hardware is busy. Needless to say, this wastes cycles and hurts interactivity with just about any scheduler you can devise. It isn't as if this is hard; on UNIX systems we did it in 1984 or thereabouts. Of course, in 1996, XFree86 would have ignored any such interfaces, in its insane quest for operating system independent user space drivers requiring no standard kernel interfaces.... (it is the second part of this where the true insanity lay). - Jim -- Jim Gettys One Laptop Per Child