From owner-freebsd-current Sun Aug 16 08:06:47 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id IAA19848 for freebsd-current-outgoing; Sun, 16 Aug 1998 08:06:47 -0700 (PDT) (envelope-from owner-freebsd-current@FreeBSD.ORG) Received: from implode.root.com (implode.root.com [198.145.90.17]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id IAA19843 for ; Sun, 16 Aug 1998 08:06:45 -0700 (PDT) (envelope-from root@implode.root.com) Received: from implode.root.com (localhost [127.0.0.1]) by implode.root.com (8.8.5/8.8.5) with ESMTP id IAA02398; Sun, 16 Aug 1998 08:06:00 -0700 (PDT) Message-Id: <199808161506.IAA02398@implode.root.com> To: Terry Lambert cc: current@FreeBSD.ORG, karl@mcs.net Subject: Re: Better VM patches (was Tentative fix for VM bug) In-reply-to: Your message of "Sun, 16 Aug 1998 14:31:59 -0000." <199808161431.HAA16709@usr08.primenet.com> From: David Greenman Reply-To: dg@root.com Date: Sun, 16 Aug 1998 08:05:59 -0700 Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG >> >John also suggested another change for detecting a case where page >> >orphans can be created. in vm_page.c, it's possible that an object >> >entry in the page insert function will overwrite an existing entry; >> >I added a DIAGNOSTIC panic to catch this when it happens. >> >> You mean that there can be multiple pages at the same offset? It would >> be bad if that happend, but I'm skeptical that it actually does. > >To elaborate: I think that the behaviour I am seeing in the "mmap'ed >file contents, on a page boundary, written to another file" case is a >result of a single page being in multiple maps. Uh, what does "single page being in multiple maps" mean exactly? What map? Pages belong to objects. A page can belong to only one object (there's only one set of list pointers, so nothing else is possible. :-)). If you see some of one file show up in another, then this suggests to me that a bzero isn't happening when it needs to, resulting in stale cached file data being considered valid. I have a suggestion. Let's not throw out random guesses about what may or may not be a problem. Let's actually understand the issue thoroghly, come up with a fix, and then tell people all about it. -DG David Greenman Co-founder/Principal Architect, The FreeBSD Project To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message