Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262540AbUCCSiX (ORCPT ); Wed, 3 Mar 2004 13:38:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262542AbUCCSiX (ORCPT ); Wed, 3 Mar 2004 13:38:23 -0500 Received: from ppp-217-133-42-200.cust-adsl.tiscali.it ([217.133.42.200]:12041 "EHLO dualathlon.random") by vger.kernel.org with ESMTP id S262540AbUCCSiV (ORCPT ); Wed, 3 Mar 2004 13:38:21 -0500 Date: Wed, 3 Mar 2004 19:39:01 +0100 From: Andrea Arcangeli To: Dave McCracken Cc: "Martin J. Bligh" , linux-kernel@vger.kernel.org Subject: Re: 230-objrmap fixes for 2.6.3-mjb2 Message-ID: <20040303183901.GU4922@dualathlon.random> References: <20040303070933.GB4922@dualathlon.random> <20040303025820.2cf6078a.akpm@osdl.org> <7440000.1078328791@[10.10.2.4]> <20040303165746.GO4922@dualathlon.random> <10500000.1078333658@[10.1.1.4]> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <10500000.1078333658@[10.1.1.4]> User-Agent: Mutt/1.4.1i X-GPG-Key: 1024D/68B9CB43 13D9 8355 295F 4823 7C49 C012 DFA1 686E 68B9 CB43 X-PGP-Key: 1024R/CB4660B9 CC A0 71 81 F4 A0 63 AC C0 4B 81 1D 8C 15 C8 E5 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1703 Lines: 33 On Wed, Mar 03, 2004 at 11:07:39AM -0600, Dave McCracken wrote: > > --On Wednesday, March 03, 2004 17:57:46 +0100 Andrea Arcangeli > wrote: > > >> There was talk at one point of moving the "unswappable" state down into > >> the struct page. Is that still realistic? It would seem rather more > >> efficient, but I forget what problem we ran into with it. > > > > that already exists and it's PG_reserved, but it's inefficient compared > > to VM_RESERVED, since it forces the vm to check all ptes. > > What we've actually discussed before was more along the lines of PG_locked > to match VM_LOCKED, but the main idea was to be able to skip over > ineligible pages without having ot look up their mappings during pageout. I'm not very excited using PG_locked for that, that doesn't only mean "unswappable", it means also that the page is under I/O (or uner some other operation that needs serialization like unmapping the page) which is quite a different concept from VM_LOCKED. a wait_on_page would deadlock on such a PG_locked page, while wait_on_page on a page of a mlocked vma doesn't normally deadlock. But I see what you want to do here, and PG_reserved would be too much for that since it changes the semantics for cow and free_pages, but PG_locked doesn't look good enough either, the VM_LOCKED and PG_locked concept is quite different, PG_reserved and VM_RESERVED is quite close instead (except for the page->count accounting). - 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/