Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263094AbUKTDln (ORCPT ); Fri, 19 Nov 2004 22:41:43 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263092AbUKTDkR (ORCPT ); Fri, 19 Nov 2004 22:40:17 -0500 Received: from smtp203.mail.sc5.yahoo.com ([216.136.129.93]:20376 "HELO smtp203.mail.sc5.yahoo.com") by vger.kernel.org with SMTP id S263099AbUKTDhK (ORCPT ); Fri, 19 Nov 2004 22:37:10 -0500 Message-ID: <419EBBE0.4010303@yahoo.com.au> Date: Sat, 20 Nov 2004 14:37:04 +1100 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.2) Gecko/20040820 Debian/1.7.2-4 X-Accept-Language: en MIME-Version: 1.0 To: William Lee Irwin III CC: Linus Torvalds , Christoph Lameter , akpm@osdl.org, Benjamin Herrenschmidt , 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 References: <419D581F.2080302@yahoo.com.au> <419D5E09.20805@yahoo.com.au> <1100848068.25520.49.camel@gaston> <20041120020306.GA2714@holomorphy.com> In-Reply-To: <20041120020306.GA2714@holomorphy.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1362 Lines: 31 William Lee Irwin III wrote: > 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. > Hang on, let's come back to this... We already have unprivileged do-for-each-thread triggers in the proc code. It's in do_task_stat, even. Rss reporting would basically just involve one extra addition within that loop. So... hmm, I can't see a problem with it. - 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/