From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [BUG] linux-2.6.28-rc3 regression: IRQ smp_affinities not respected Date: Wed, 05 Nov 2008 07:33:21 +0100 Message-ID: <49113E31.8080106@cosmosbay.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: linux kernel , Linux Netdev List Return-path: Received: from gw1.cosmosbay.com ([86.65.150.130]:48708 "EHLO gw1.cosmosbay.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750807AbYKEGdc (ORCPT ); Wed, 5 Nov 2008 01:33:32 -0500 Sender: netdev-owner@vger.kernel.org List-ID: Hi all One more problem it seems on 2.6.28-rc3 I wanted to get maximal throughput from my machine on a network bench with 3 Gigabit links delivering 600.000 packets per second, so I tried to play with smp_affinity to dedicate one CPU for each NIC. It worked with 2.6.27, so there is a regression on this part. Unfortunatly, git bisect is nearly impossible for me as after two steps the resulting kernel doesnt event boot on this machine (same for oprofile regression I mentioned earlier) # grep eth1 /proc/interrupts 45: 20425 20418 20445 20441 20345 20349 20384 20397 PCI-MSI-edge eth1 # cat /proc/irq/45/smp_affinity ff # echo 1 >/proc/irq/45/smp_affinity # cat /proc/irq/45/smp_affinity 01 # grep eth1 /proc/interrupts 45: 20928 20920 20943 20940 20845 20847 20887 20898 PCI-MSI-edge eth1 # grep eth1 /proc/interrupts 45: 21037 21030 21053 21049 20953 20956 20997 21007 PCI-MSI-edge eth1 # grep eth1 /proc/interrupts 45: 21141 21134 21156 21154 21057 21059 21101 21110 PCI-MSI-edge eth1 You can see interrupts keep being spreaded on all CPUS instead of CPU0 only. That *kills* performance on high end routers and servers. 07:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM5708S Gigabit Ethernet (rev 12) Subsystem: Hewlett-Packard Company NC373i Integrated Multifunction Gigabit Server Adapter Flags: bus master, 66Mhz, medium devsel, latency 64, IRQ 45 Memory at fa000000 (64-bit, non-prefetchable) [size=32M] [virtual] Expansion ROM at d1000000 [disabled] [size=16K] Capabilities: [40] PCI-X non-bridge device. Capabilities: [48] Power Management version 2 Capabilities: [50] Vital Product Data Capabilities: [58] Message Signalled Interrupts: 64bit+ Queue=0/0 Enable+ bnx2 driver Thanks