Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755951Ab1C3OHc (ORCPT ); Wed, 30 Mar 2011 10:07:32 -0400 Received: from mga01.intel.com ([192.55.52.88]:64250 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754812Ab1C3OHc (ORCPT ); Wed, 30 Mar 2011 10:07:32 -0400 Message-Id: X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.63,269,1299484800"; d="scan'208";a="903558723" Date: Wed, 30 Mar 2011 15:07:28 +0100 To: Jerome Glisse Subject: Re: GEM-related desktop sluggishness due to linear-time arch_get_unmapped_area_topdown() Cc: Dave Airlie , r6144 , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org References: <1301310995.5615.92.camel@wangqingchuan> <1301336010.2217.20.camel@workstation> <1301409864.5615.98.camel@wangqingchuan> <1301421664.2151.12.camel@Portable-Work> <20110329202608.GA3454@viiv.ffwll.ch> <849307$c7qtj5@azsmga001.ch.intel.com> From: Chris Wilson In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2208 Lines: 42 On Wed, 30 Mar 2011 09:28:07 -0400, Jerome Glisse wrote: > On Wed, Mar 30, 2011 at 3:32 AM, Chris Wilson wrote: > > On Wed, 30 Mar 2011 07:57:49 +1000, Dave Airlie wrote: > >> On Wed, Mar 30, 2011 at 7:04 AM, Jerome Glisse wrote: > >> > What i had in mind was something little bit more advance that pwrite, > >> > somethings that would take width,height,pitch of userpage and would be > >> > able to perform proper blit. But yes pwrite in intel is kind of > >> > limited. > >> > >> TTM has support for userpage binding we just don't use it. > > > > Yes, and I've been experimenting with the same in GEM to great effect in > > the DDX. The complication remains in managing the CPU synchronisation, > > which suggests that it would only be useful for STREAM_DRAW objects (and > > perhaps the sub-region updates to STATIC_DRAW). (And for readback, if > > retrieving the data were the actual bottleneck.) > > What do you mean by CPU synchronisation ? In what i had in mind the > upload/download would block userspace until operation is, this would > make upload/dowload barrier of course it doesn't play well with > usecase where you keep uploading/downloading (idea to aleviate that is > to allow several download/upload in one ioctl call). Yes, that is the issue: having to control access to the user pages whilst they are in use by the GPU. A completely synchronous API for performing a single pwrite with the blitter is too slow, much slower than doing an uncached write with the CPU and queueing up multiple blits (as we currently do). The API I ended up with for the pwrite using the BLT was to specify a 2D region (addr, width, height, stride, flags etc) and list of clip rects. At which point I grew disenchanted, and realised that simply creating a bo for mapping user pages was the far better solution. -Chris -- Chris Wilson, Intel Open Source Technology Centre -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/