From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 19 Nov 2004 11:59:03 -0800 (PST) From: Linus Torvalds 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: owner-linux-mm@kvack.org Return-Path: 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 List-ID: 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 -- 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