Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755706AbaJHVh0 (ORCPT ); Wed, 8 Oct 2014 17:37:26 -0400 Received: from mga09.intel.com ([134.134.136.24]:4215 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751067AbaJHVhY (ORCPT ); Wed, 8 Oct 2014 17:37:24 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.04,680,1406617200"; d="scan'208";a="615425572" Message-ID: <5435AE71.60304@linux.intel.com> Date: Wed, 08 Oct 2014 14:36:49 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.1 MIME-Version: 1.0 To: Chris Wilson , Chuck Ebbert CC: linux-kernel@vger.kernel.org, Masami Hiramatsu , Jiri Kosina , Steven Rostedt , Jason Baron , yrl.pp-manager.tt@hitachi.com, Borislav Petkov , Ingo Molnar , Daniel Vetter , x86@kernel.org, Thomas Gleixner Subject: Re: i915.ko WC writes are slow after ea8596bb2d8d379 References: <20141008090336.GD12897@nuc-i3427.alporthouse.com> <20141008051059.65566251@as> <20141008194955.GF12897@nuc-i3427.alporthouse.com> In-Reply-To: <20141008194955.GF12897@nuc-i3427.alporthouse.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/08/2014 12:49 PM, Chris Wilson wrote: > > Indeed, this appears to be the explanation. (And here I thought PAT > superseded mtrrs - i915.ko stopped trying to use assign an mtrr for its > GTT quite a while ago.) > > Replacing the stop_machine there with on_each_cpu does the trick: > It should, but there seem to be quite a few drivers which still muck with MTRRs. However, i915 is not one of them, it calls io_mapping_create_wc() followed by arch_phys_wc_add(), so I'm wondering what the heck is going on here. > Naively I would say that we lost the wc on our ioremap. > /sys/kernel/debug/x86/pat_memtype_list remained the same across repeated > runs. Could you tell me what the above looks like? -hpa -- 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/