From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755458AbXHBCPe (ORCPT ); Wed, 1 Aug 2007 22:15:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751525AbXHBCP1 (ORCPT ); Wed, 1 Aug 2007 22:15:27 -0400 Received: from mx1.suse.de ([195.135.220.2]:45631 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751449AbXHBCP0 (ORCPT ); Wed, 1 Aug 2007 22:15:26 -0400 Date: Thu, 2 Aug 2007 04:15:25 +0200 From: Nick Piggin To: Ingo Molnar , Linus Torvalds Cc: Andrew Morton , Linux Kernel Mailing List Subject: lmbench ctxsw regression with CFS Message-ID: <20070802021525.GC15595@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, I didn't follow all of the scheduler debates and flamewars, so apologies if this was already covered. Anyway. lmbench 3 lat_ctx context switching time with 2 processes bound to a single core increases by between 25%-35% on my Core2 system (didn't do enough runs to get more significance, but it is around 30%). The problem bisected to the main CFS commit. I was really hoping that a smaller runqueue data structure could actually increase performance with the common case of small numbers of tasks :( I assume this was a known issue before CFS was merged. Do you know what is causing the slowdown? Any plans to fix it? Thanks, Nick