From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2EDB2C43441 for ; Mon, 12 Nov 2018 14:36:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 021BE224E0 for ; Mon, 12 Nov 2018 14:36:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 021BE224E0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729496AbeKMA3o (ORCPT ); Mon, 12 Nov 2018 19:29:44 -0500 Received: from mx2.suse.de ([195.135.220.15]:36168 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727033AbeKMA3n (ORCPT ); Mon, 12 Nov 2018 19:29:43 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 409E4B131; Mon, 12 Nov 2018 14:36:10 +0000 (UTC) Message-ID: <1542033367.2661.33.camel@suse.de> Subject: Re: Performance regression in ast drm driver From: Jean Delvare To: David Airlie Cc: christian.koenig@amd.com, "Iwai, Takashi" , dri-devel , linux-kernel Date: Mon, 12 Nov 2018 15:36:07 +0100 In-Reply-To: References: <20181101162707.598c1718@endymion> <20181108130509.3b2d42ff@endymion> Organization: Suse Linux Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi David, On Fri, 2018-11-09 at 10:04 +1000, David Airlie wrote: > On Thu, Nov 8, 2018 at 10:05 PM Jean Delvare wrote: > > > > On Thu, 1 Nov 2018 16:27:07 +0100, Jean Delvare wrote: > > > Hi David, > > > > > > The following commit: > > > > > > commit 7cf321d118a825c1541b43ca45294126fd474efa > > > Author: Dave Airlie > > > Date: Mon Oct 24 15:37:48 2016 +1000 > > > > > > drm/drivers: add support for using the arch wc mapping API. > > > > > > is causing a huge performance regression for the ast drm driver. In a > > > text console, if I call "cat" on a large text file, it takes almost > > > twice as much time to be displayed and scrolled completely. > > > > > > Can you please check that the ast driver portion of that commit is both > > > correct and complete? > > > > And in the meantime, what bad will happen if we just revert the ast > > portion of that commit? > > This seems likely to be a hw problem with PCI writes to the AST "GPU", > since it's just some sort of RAM + ARM on the end of a PCIE bus, we've > definitely seen possible issues in the past with write combining > around some of the mga GPUs with some CPUs. Takashi asked me to compare the contents of /sys/kernel/debug/x86/pat_memtype_list before and after the commit above. Before the commit, we have: uncached-minus @ 0xfafe0000-0xfb000000 uncached-minus @ 0xfb000000-0xfb005000 write-combining @ 0xfb005000-0xfb584000 After the commit, we have: uncached-minus @ 0xfafe0000-0xfb000000 uncached-minus @ 0xfb000000-0xfb005000 uncached-minus @ 0xfb000000-0xfb800000 uncached-minus @ 0xfb005000-0xfb584000 The corresponding lines in /proc/iomem are: f0000000-fed8ffff : PCI Bus 0000:00   faf00000-fb7fffff : PCI Bus 0000:01     fafe0000-faffffff : 0000:01:01.0     fb000000-fb7fffff : 0000:01:01.0 Does it help? Is the change of type expected? Is it not a problem that one of the ranges is overlapping with 2 other ranges? -- Jean Delvare SUSE L3 Support