Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752618AbZK1SKS (ORCPT ); Sat, 28 Nov 2009 13:10:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751904AbZK1SKR (ORCPT ); Sat, 28 Nov 2009 13:10:17 -0500 Received: from mta2.srv.hcvlny.cv.net ([167.206.4.197]:49827 "EHLO mta2.srv.hcvlny.cv.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751737AbZK1SKQ (ORCPT ); Sat, 28 Nov 2009 13:10:16 -0500 Date: Sat, 28 Nov 2009 13:10:21 -0500 From: Michael Breuer Subject: Re: Problem? intel_iommu=off; perf top shows acpi_os_read_port as extremely busy In-reply-to: <20091128094530.0ede7b1a@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: <4B11678D.8020601@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> User-Agent: Thunderbird 2.0.0.23 (Windows/20090812) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1861 Lines: 49 Ok - my only question then is why things appear so different with intel_iommu enabled. Arjan van de Ven wrote: > On Sat, 28 Nov 2009 08:18:08 +0100 > Ingo Molnar wrote: > > >> * Michael Breuer wrote: >> >> >>> Having given up for now on VT-D, I rebooted 2.6.38 rc8 with >>> intel_iommu=off. Whilst my myriad of broken bios issues cleared, I >>> now see in perf top acpi_os_read_port as continually the busiest >>> function. With intel_iommu enabled, _spin_lock was always on top, >>> and nothing else was notable. >>> >>> This seems odd to me, perhaps this will make sense to someone else. >>> >>> FWIW, I'm running on an Asus p6t deluxe v2; ht enabled; no errors >>> or oddities in dmesg or /var/log/messages. >>> >> Could you post the perf top output please? >> >> Also, could you also post the output of: >> >> perf stat -a --repeat 10 sleep 1 >> >> this will show us how idle the system is. (My guess is that your >> system is idle and perf top shows acpi_os_read_port because the >> system goes to idle via ACPI methods and PIO is slow. In that case >> all is nominal and your system is fine. But it's hard to tell without >> more details.) >> >> > > yeah the os_read_port is part of the idle loop, so if your system is > idle it'll show up big.... not much we can optimize there though... > -- > 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/ > -- 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/