From mboxrd@z Thu Jan 1 00:00:00 1970 From: William Lee Irwin III Date: Sat, 20 Nov 2004 02:03:06 +0000 Subject: Re: page fault scalability patch V11 [0/7]: overview Message-Id: <20041120020306.GA2714@holomorphy.com> List-Id: References: <419D581F.2080302@yahoo.com.au> <419D5E09.20805@yahoo.com.au> <1100848068.25520.49.camel@gaston> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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 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