From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765372AbXGZMD2 (ORCPT ); Thu, 26 Jul 2007 08:03:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755004AbXGZMC7 (ORCPT ); Thu, 26 Jul 2007 08:02:59 -0400 Received: from smtp4-g19.free.fr ([212.27.42.30]:34581 "EHLO smtp4-g19.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751982AbXGZMCy (ORCPT ); Thu, 26 Jul 2007 08:02:54 -0400 Message-ID: <46A88D5E.9060204@free.fr> Date: Thu, 26 Jul 2007 14:02:38 +0200 From: John Sigler User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.8) Gecko/20061108 SeaMonkey/1.0.6 MIME-Version: 1.0 To: Len Brown CC: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: Pin-pointing the root of unusual application latencies References: <469600F7.3060603@free.fr> <20070725133835.GA17616@elte.hu> <46A758B5.9070602@free.fr> <200707251309.54240.lenb@kernel.org> <46A85CE9.7070506@free.fr> <46A87B3D.3020003@free.fr> In-Reply-To: <46A87B3D.3020003@free.fr> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > John Sigler wrote: > >> Len Brown wrote: >> >>> John Sigler wrote: >>> >>>> # cat /proc/interrupts >>>> CPU0 >>>> 0: 37 XT-PIC-XT timer >>>> 1: 2 XT-PIC-XT i8042 >>>> 2: 0 XT-PIC-XT cascade >>>> 7: 0 XT-PIC-XT acpi >>>> 10: 175 XT-PIC-XT eth2, Dta1xx >>>> 11: 1129 XT-PIC-XT eth0 >>>> 12: 4 XT-PIC-XT eth1 >>>> 14: 21482 XT-PIC-XT ide0 >>>> NMI: 0 >>>> LOC: 161632 >>>> ERR: 0 >>>> MIS: 0 >>>> >>>> IRQ 10 is shared between a NIC and an I/O board. >>>> >>>> For eth2, the kernel said: >>>> ACPI: PCI Interrupt 0000:00:0a.0[A] -> Link [LNKC] >>>> -> GSI 10 (level, low) -> IRQ 10 >>>> >>>> For Dta1xx, the kernel said: >>>> ACPI: PCI Interrupt 0000:02:0e.0[A] -> Link [LNKC] >>>> -> GSI 10 (level, low) -> IRQ 10 >>>> >>>> Is it possible to avoid the two boards sharing IRQ 10? >>> >>> Maybe. In this configuration, INTA of the two devices >>> is physically connected to the same wire on the device-side >>> of the interrupt re-mapper -- so you'd have to change the configuration. >>> If you have an IOAPIC and can enable it, that will not hurt -- >> >> I believe this board does not provide an IO-APIC. >> Even the LAPIC is disabled in the BIOS. >> (Why would they do that??) >> >>> though unless something else changes, these devices are still >>> tied together on the device-side of the mapper. >>> So if you can physically move one of the devices to another slot >>> that is your best bet. > > The NICs are on-board, therefore it is not possible to move them. > > The motherboard only has one PCI slot, so the manufacturer includes > a backplane (is that what it's called?) to provide two PCI slots. > > The results I've given so far were with the I/O board inserted in > the bottom slot. If it is inserted in the top slot, the results are > different indeed. > > # cat /proc/interrupts > CPU0 > 0: 37 XT-PIC-XT timer > 1: 2 XT-PIC-XT i8042 > 2: 0 XT-PIC-XT cascade > 5: 20270 XT-PIC-XT Dta1xx > 7: 0 XT-PIC-XT acpi > 10: 4 XT-PIC-XT eth2 > 11: 2639 XT-PIC-XT eth0 > 12: 4 XT-PIC-XT eth1 > 14: 13984 XT-PIC-XT ide0 > NMI: 0 > LOC: 518501 > ERR: 0 > MIS: 0 With a 4-port NIC (instead of the I/O board) inserted in the top slot. # cat /proc/interrupts CPU0 0: 37 XT-PIC-XT timer 1: 2 XT-PIC-XT i8042 2: 0 XT-PIC-XT cascade 5: 0 XT-PIC-XT eth3 7: 0 XT-PIC-XT acpi 10: 4 XT-PIC-XT eth1, eth5 11: 4 XT-PIC-XT eth2, eth6 12: 265 XT-PIC-XT eth0, eth4 14: 12726 XT-PIC-XT ide0 NMI: 0 LOC: 12704 ERR: 0 MIS: 0 With the 4-port NIC inserted in the bottom slot. # cat /proc/interrupts CPU0 0: 37 XT-PIC-XT timer 1: 2 XT-PIC-XT i8042 2: 0 XT-PIC-XT cascade 5: 4 XT-PIC-XT eth2, eth3 7: 0 XT-PIC-XT acpi 10: 99 XT-PIC-XT eth0, eth5 11: 4 XT-PIC-XT eth1, eth6 12: 0 XT-PIC-XT eth4 14: 12138 XT-PIC-XT ide0 NMI: 0 LOC: 3554 ERR: 0 MIS: 0 As far as I understand, this board has 4 interrupt lines, and they are mapped (by the BIOS? by Linux?) to ISA IRQs 5, 10, 11, and 12. If I insert another 4-port NIC in the remaining slot, eth7 through eth10 will spread to these IRQs. Correct? Suppose 3 NICs share the same interrupt line, and each receives 1500 packets per second. (I suppose that translates to 1500 interrupt requests per second.) Will the system cope with 4500 interrupt requests from 3 different devices on the same interrupt line? How different is it from 4500 interrupt requests from a single device not sharing the line? Regards.