From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261452AbVF1Mpp (ORCPT ); Tue, 28 Jun 2005 08:45:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261455AbVF1Mpp (ORCPT ); Tue, 28 Jun 2005 08:45:45 -0400 Received: from hellhawk.shadowen.org ([80.68.90.175]:53254 "EHLO hellhawk.shadowen.org") by vger.kernel.org with ESMTP id S261452AbVF1Mpj (ORCPT ); Tue, 28 Jun 2005 08:45:39 -0400 Message-ID: <42C14662.40809@shadowen.org> Date: Tue, 28 Jun 2005 13:45:22 +0100 From: Andy Whitcroft User-Agent: Debian Thunderbird 1.0.2 (X11/20050602) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Nick Piggin CC: linux-kernel , Linux Memory Management Subject: Re: [patch 2] mm: speculative get_page References: <42BF9CD1.2030102@yahoo.com.au> <42BF9D67.10509@yahoo.com.au> <42BF9D86.90204@yahoo.com.au> In-Reply-To: <42BF9D86.90204@yahoo.com.au> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Nick Piggin wrote: > #define PG_free 20 /* Page is on the free lists */ > +#define PG_freeing 21 /* PG_refcount about to be freed */ Wow this needs two new page bits. That might be a problem ongoing. There are only 24 of these puppies and this takes us to just two remaining. Do we really need _two_ to track free? One obvious area of overlap might be the PG_nosave_free which seems to be set on free pages for software suspend. Perhaps that and PG_free will be equivalent in intent (though maintained differently) and allow us to recover a bit? There are a couple of bits which imply ownership such as PG_slab, PG_swapcache and PG_reserved which to my mind are all exclusive. Perhaps those plus the PG_free could be combined into a owner field. I am unsure if the PG_freeing can be 'backed out' if not it may also combine? Mumble ... -apw