Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751504AbZK3FMN (ORCPT ); Mon, 30 Nov 2009 00:12:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751127AbZK3FMN (ORCPT ); Mon, 30 Nov 2009 00:12:13 -0500 Received: from mta1.srv.hcvlny.cv.net ([167.206.4.196]:58573 "EHLO mta1.srv.hcvlny.cv.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751062AbZK3FMM (ORCPT ); Mon, 30 Nov 2009 00:12:12 -0500 Date: Mon, 30 Nov 2009 00:11:51 -0500 From: Michael Breuer Subject: Re: Problem? intel_iommu=off; perf top shows acpi_os_read_port as extremely busy In-reply-to: <20091129124731.7d0c9b45@infradead.org> To: Arjan van de Ven Cc: Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Len Brown , Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org Message-id: <4B135417.1080302@majjas.com> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7BIT References: <4B106CC0.4050406@majjas.com> <20091128071808.GA32183@elte.hu> <20091128094530.0ede7b1a@infradead.org> <4B11678D.8020601@majjas.com> <20091129124731.7d0c9b45@infradead.org> User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.4pre) Gecko/20091109 Fedora/3.0-3.10.b4.fc12 Thunderbird/3.0b4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2398 Lines: 60 Ok - one more rather odd (to me) data point... I started playing around with various settings, and traced the calls to acpi_os_read_port. To summarize: With intel_iommu=off, I see a large percentage of calls to acpi_os_read_port resulting from user apps (portsentry is #1). With intel_iommu=on, NONE of trace points to any user apps - all derive from the idle loop. To make things more interesting, when I enable intel_iommu and disable vt-d in bios, the system performs much better (20% improvement in glxgears, for example), perf top looks like this: ------------------------------------------------------------------------------ PerfTop: 4863 irqs/sec kernel:62.7% [100000 cycles], (all, 8 CPUs) ------------------------------------------------------------------------------ samples pcnt kernel function _______ _____ _______________ 2213.00 - 5.5% : acpi_idle_enter_bm 2001.00 - 5.0% : acpi_os_read_port 1544.00 - 3.9% : _spin_lock_irqsave 1075.00 - 2.7% : ioread32 928.00 - 2.3% : find_busiest_group 851.00 - 2.1% : _spin_unlock_irqrestore 823.00 - 2.1% : hpet_next_event 810.00 - 2.0% : tg_shares_up 655.00 - 1.6% : fget_light 641.00 - 1.6% : schedule 639.00 - 1.6% : tick_nohz_stop_sched_tick 638.00 - 1.6% : sub_preempt_count 634.00 - 1.6% : add_preempt_count 548.00 - 1.4% : do_sys_poll 446.00 - 1.1% : trace_hardirqs_off And additionally, one recurring boot warning I've seen since I first booted this box has disappeared - first boot message of IRQ16 disabled. I'm thinking that bad VT-D bios is causing trouble even when intel_iommu is disabled. On 11/29/2009 03:47 PM, Arjan van de Ven wrote: > On Sat, 28 Nov 2009 13:10:21 -0500 > Michael Breuer wrote: > > >> Ok - my only question then is why things appear so different with >> intel_iommu enabled. >> > something else is even more expensive then :0 > > > -- 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/