From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261608AbUKSUCz (ORCPT ); Fri, 19 Nov 2004 15:02:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261613AbUKSUAc (ORCPT ); Fri, 19 Nov 2004 15:00:32 -0500 Received: from fw.osdl.org ([65.172.181.6]:2227 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S261574AbUKST7Q (ORCPT ); Fri, 19 Nov 2004 14:59:16 -0500 Date: Fri, 19 Nov 2004 11:59:03 -0800 (PST) From: Linus Torvalds To: Christoph Lameter cc: akpm@osdl.org, Benjamin Herrenschmidt , Nick Piggin , Hugh Dickins , linux-mm@kvack.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: page fault scalability patch V11 [0/7]: overview In-Reply-To: Message-ID: References: <419D581F.2080302@yahoo.com.au> <419D5E09.20805@yahoo.com.au> <1100848068.25520.49.camel@gaston> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 19 Nov 2004, Christoph Lameter wrote: > > Note that I have posted two other approaches of dealing with the rss problem: You could also make "rss" be a _signed_ integer per-thread. When unmapping a page, you decrement one of the threads that shares the mm (doesn't matter which - which is why the per-thread rss may go negative), and when mapping a page you increment it. Then, anybody who actually wants a global rss can just iterate over threads and add it all up. If you do it under the mmap_sem, it's stable, and if you do it outside the mmap_sem it's imprecise but stable in the long term (ie errors never _accumulate_, like the non-atomic case will do). Does anybody care enough? Maybe, maybe not. It certainly sounds a hell of a lot better than the periodic scan. Linus