Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262119AbUKVXQP (ORCPT ); Mon, 22 Nov 2004 18:16:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261867AbUKVXNh (ORCPT ); Mon, 22 Nov 2004 18:13:37 -0500 Received: from fw.osdl.org ([65.172.181.6]:30385 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S261224AbUKVXMW (ORCPT ); Mon, 22 Nov 2004 18:12:22 -0500 Date: Mon, 22 Nov 2004 15:16:28 -0800 From: Andrew Morton To: Christoph Lameter Cc: hugh@veritas.com, torvalds@osdl.org, benh@kernel.crashing.org, nickpiggin@yahoo.com.au, linux-mm@kvack.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: deferred rss update instead of sloppy rss Message-Id: <20041122151628.77ab87ca.akpm@osdl.org> In-Reply-To: References: <20041122141148.1e6ef125.akpm@osdl.org> <20041122144507.484a7627.akpm@osdl.org> X-Mailer: Sylpheed version 0.9.7 (GTK+ 1.2.10; i586-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1032 Lines: 26 Christoph Lameter wrote: > > On Mon, 22 Nov 2004, Andrew Morton wrote: > > > > The page fault code only increments rss. For larger transactions that > > > increase / decrease rss significantly the page_table_lock is taken and > > > mm->rss is updated directly. So no > > > gross inaccuracies can result. > > > > Sure. Take a million successive pagefaults and mm->rss is grossly > > inaccurate. Hence my suggestion that it be spilled into mm->rss > > periodically. > > It is spilled into mm->rss periodically. That is the whole point of the > patch. > > The timer tick occurs every 1 ms. That only works if the task happens to have the CPU when the timer tick occurs. There remains no theoretical upper bound to the error in mm->rss, and that's very easy to fix. - 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/