From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263733AbUG2HrW (ORCPT ); Thu, 29 Jul 2004 03:47:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266580AbUG2HrW (ORCPT ); Thu, 29 Jul 2004 03:47:22 -0400 Received: from mx1.redhat.com ([66.187.233.31]:34009 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S263733AbUG2HrU (ORCPT ); Thu, 29 Jul 2004 03:47:20 -0400 Message-ID: <4108AB1A.1050706@redhat.com> Date: Thu, 29 Jul 2004 00:45:30 -0700 From: Ulrich Drepper Organization: Red Hat, Inc. User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8a3) Gecko/20040728 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Peter Chubb CC: viro@parcelfarce.linux.theplanet.co.uk, "David S. Miller" , Chris Wedgwood , linux-kernel@vger.kernel.org Subject: Re: stat very inefficient References: <233602095@toto.iv> <16648.10711.200049.616183@wombat.chubb.wattle.id.au> <20040728154523.20713ef1.davem@redhat.com> <20040729000837.GA24956@taniwha.stupidest.org> <20040728171414.5de8da96.davem@redhat.com> <20040729002924.GK12308@parcelfarce.linux.theplanet.co.uk> <16648.42669.907048.112765@wombat.chubb.wattle.id.au> In-Reply-To: <16648.42669.907048.112765@wombat.chubb.wattle.id.au> X-Enigmail-Version: 0.85.0.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Peter Chubb wrote: > With hot cache the system time is really small. But this is not all you'll have to look at. Single application performs does not really tell the whole story. If you touch more memory, more cache is used. In SMP machines the cost of cacheline transfers are added. And in multi-core processors the cores even share some cache which means every bit used might decrease system performance ever so slightly. If the added complexity is manageable the avoided memory operations should be a win even if you cannot directly measure it. -- ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖