From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933934AbXDBGa1 (ORCPT ); Mon, 2 Apr 2007 02:30:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933928AbXDBGa0 (ORCPT ); Mon, 2 Apr 2007 02:30:26 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:34763 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933925AbXDBGaZ (ORCPT ); Mon, 2 Apr 2007 02:30:25 -0400 Date: Mon, 2 Apr 2007 08:30:18 +0200 From: Ingo Molnar To: Nivedita Singhvi Cc: Dave Sperry , linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, netdev Subject: Re: Poor UDP performance using 2.6.21-rc5-rt5 Message-ID: <20070402063018.GA10209@elte.hu> References: <461004CE.1030009@ieee.org> <461010F9.7040706@us.ibm.com> <20070402055509.GC3284@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070402055509.GC3284@elte.hu> User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.0.3 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Ingo Molnar wrote: > one thing to check would be whether both kernels use the same > clocksource, via: > > cat /sys/devices/system/clocksource/clocksource0/current_clocksource > > but at first sight there's no clocksource related overhead in the > oprofile. i've started a similar netperf test and clocksource overhead dominates the profile: 5553 handle_fasteoi_irq 26.1934 5940 nv_start_xmit_optimized 6.6892 6014 ack_ioapic_quirk_irq 44.5481 7591 mask_IO_APIC_irq 154.9184 8155 __copy_from_user_ll 37.4083 13371 io_apic_base 417.8438 13565 get_next_timer_interrupt 29.7478 13966 __modify_IO_APIC_irq 151.8043 14213 do_irqd 22.7045 17834 unmask_IO_APIC_irq 424.6190 20503 __schedule 6.4455 48456 cpu_idle 180.8060 170001 acpi_pm_read 8947.4211 517107 total 0.1566 acpi_pm_read() amounts to 32% overhead! i'm not sure why the oprofile results show no clocksource overhead - the -rt kernel typically uses the pm-timer on Opterons. to get more comparable results, boot the vanilla kernel with the "apicpmtimer" boot option, and/or do this after bootup: echo acpi_pm > /sys/devices/system/clocksource/clocksource0/current_clocksource Ingo