From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <419EBBE0.4010303@yahoo.com.au> Date: Sat, 20 Nov 2004 14:37:04 +1100 From: Nick Piggin MIME-Version: 1.0 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: owner-linux-mm@kvack.org Return-Path: 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 List-ID: 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org