From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262743AbUKTCLQ (ORCPT ); Fri, 19 Nov 2004 21:11:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261712AbUKTCFS (ORCPT ); Fri, 19 Nov 2004 21:05:18 -0500 Received: from holomorphy.com ([207.189.100.168]:25728 "EHLO holomorphy.com") by vger.kernel.org with ESMTP id S261525AbUKTCDX (ORCPT ); Fri, 19 Nov 2004 21:03:23 -0500 Date: Fri, 19 Nov 2004 18:03:06 -0800 From: William Lee Irwin III To: Linus Torvalds Cc: Christoph Lameter , 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 Message-ID: <20041120020306.GA2714@holomorphy.com> 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 Content-Disposition: inline In-Reply-To: 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 On Fri, Nov 19, 2004 at 11:59:03AM -0800, Linus Torvalds wrote: > 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. Unprivileged triggers for full-tasklist scans are NMI oops material. -- wli