From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268026AbUIPMTi (ORCPT ); Thu, 16 Sep 2004 08:19:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268021AbUIPMTi (ORCPT ); Thu, 16 Sep 2004 08:19:38 -0400 Received: from holomorphy.com ([207.189.100.168]:63907 "EHLO holomorphy.com") by vger.kernel.org with ESMTP id S268026AbUIPMSr (ORCPT ); Thu, 16 Sep 2004 08:18:47 -0400 Date: Thu, 16 Sep 2004 05:17:47 -0700 From: William Lee Irwin III To: Denis Vlasenko Cc: linux-kernel@vger.kernel.org Subject: Re: top hogs CPU in 2.6: kallsyms_lookup is very slow Message-ID: <20040916121747.GQ9106@holomorphy.com> References: <200409161428.27425.vda@port.imtp.ilyichevsk.odessa.ua> <20040916114515.GP9106@holomorphy.com> <200409161457.08544.vda@port.imtp.ilyichevsk.odessa.ua> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200409161457.08544.vda@port.imtp.ilyichevsk.odessa.ua> Organization: The Domain of Holomorphy User-Agent: Mutt/1.5.6+20040722i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org At some point in the past, I wrote: >> As for all syscalls/etc. being slower by 50%-100%, I suggest toning On Thu, Sep 16, 2004 at 02:57:08PM +0300, Denis Vlasenko wrote: > s/all/many/: > uname <0.000142> ? ? ? ? ? ? ? uname <0.000217> 25% slower > brk <0.000176> ? ? ? ? ? ? ? ? brk <0.000174> no change > open <0.000218> ? ? ? ? ? ? ? ?open <0.000335> 33% slower > fstat64 <0.000104> ? ? ? ? ? ? fstat64 <0.000191> 90% slower > or maybe strace simply isn't very accurate and adds signinficant > noise to the measured delta? Could you try to estimate the resolution of whatever timer strace uses? At some point in the past, I wrote: >> down HZ (we desperately need to go tickless) and seeing if it persists. >> Also please check that time isn't twice as fast as it should be in 2.6. On Thu, Sep 16, 2004 at 02:57:08PM +0300, Denis Vlasenko wrote: > I recompiled 2.6 with HZ=100. It's not it. > Time is running normally too. Did the kallsyms patches reduce the cpu overhead from get_wchan()? I take this to mean reducing HZ to 100 did not alleviate the syscall problems? How do microbenchmarks fare, e.g. lmbench? -- wli