Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268029AbUIPMfJ (ORCPT ); Thu, 16 Sep 2004 08:35:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268039AbUIPMc2 (ORCPT ); Thu, 16 Sep 2004 08:32:28 -0400 Received: from 168.imtp.Ilyichevsk.Odessa.UA ([195.66.192.168]:26381 "HELO port.imtp.ilyichevsk.odessa.ua") by vger.kernel.org with SMTP id S268043AbUIPMbi (ORCPT ); Thu, 16 Sep 2004 08:31:38 -0400 From: Denis Vlasenko To: William Lee Irwin III Subject: Re: top hogs CPU in 2.6: kallsyms_lookup is very slow Date: Thu, 16 Sep 2004 15:31:26 +0300 User-Agent: KMail/1.5.4 Cc: linux-kernel@vger.kernel.org References: <200409161428.27425.vda@port.imtp.ilyichevsk.odessa.ua> <200409161457.08544.vda@port.imtp.ilyichevsk.odessa.ua> <20040916121747.GQ9106@holomorphy.com> In-Reply-To: <20040916121747.GQ9106@holomorphy.com> MIME-Version: 1.0 Content-Type: text/plain; charset="koi8-r" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200409161531.26311.vda@port.imtp.ilyichevsk.odessa.ua> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1569 Lines: 42 On Thursday 16 September 2004 15:17, William Lee Irwin III wrote: > 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 I am applying them right now... > this to mean reducing HZ to 100 did not alleviate the syscall problems? Yes, it didn't help. > How do microbenchmarks fare, e.g. lmbench? I did not run them (yet). -- vda - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/