From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.8 required=5.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 590FE7D099 for ; Wed, 14 Nov 2018 22:23:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387683AbeKOI22 (ORCPT ); Thu, 15 Nov 2018 03:28:28 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:55000 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729093AbeKOI21 (ORCPT ); Thu, 15 Nov 2018 03:28:27 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=HZ9FoT/Yy3OX8C0H4qzEvYCUztlDQL9Afu/eqdCHPIU=; b=du9FHmqJIFno6bdq2AWaNBqtB q9G5S07pYfFUoBX6rUJlRGhD+Ggnu7bn0V2NmFfhXVu8PFulCAVmSvxDs0TavDbD4ApJYN3lRgZ0V ZlWGBgkro3pzJ0HRwVJWmR1Gs43gASfN1yv9csU5NIl0gjDkjNDLgwEQc6cCsJ7yDrgmV26JIWW49 r4BR52qzvTZXmaqJf9CeWtFdnwYblbPpYACYw7pEhPy6Z49PsKlypZ68tCMD4cO2d3kvDZTbxgM/5 FttHCvpncqygVXjrC5SYPJUa12r9hCJwXIjJjP3r9D4d8ShA3rwNPW3H/7/RrnojeJ3PoOHluVe1T 8qNIkPKpA==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gN3ZB-0001Va-DA; Wed, 14 Nov 2018 22:23:21 +0000 Date: Wed, 14 Nov 2018 14:23:21 -0800 From: Matthew Wilcox To: David Hildenbrand Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, devel@linuxdriverproject.org, linux-fsdevel@vger.kernel.org, linux-pm@vger.kernel.org, xen-devel@lists.xenproject.org, Jonathan Corbet , Alexey Dobriyan , Mike Rapoport , Andrew Morton , Christian Hansen , Vlastimil Babka , "Kirill A. Shutemov" , Stephen Rothwell , "Michael S. Tsirkin" , Michal Hocko , Pavel Tatashin , Alexander Duyck , Naoya Horiguchi , Miles Chen , David Rientjes Subject: Re: [PATCH RFC 2/6] mm: convert PG_balloon to PG_offline Message-ID: <20181114222321.GB1784@bombadil.infradead.org> References: <20181114211704.6381-1-david@redhat.com> <20181114211704.6381-3-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181114211704.6381-3-david@redhat.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Wed, Nov 14, 2018 at 10:17:00PM +0100, David Hildenbrand wrote: > Rename PG_balloon to PG_offline. This is an indicator that the page is > logically offline, the content stale and that it should not be touched > (e.g. a hypervisor would have to allocate backing storage in order for the > guest to dump an unused page). We can then e.g. exclude such pages from > dumps. > > In following patches, we will make use of this bit also in other balloon > drivers. While at it, document PGTABLE. Thank you for documenting PGTABLE. I didn't realise I also had this document to update when I added PGTABLE. > +++ b/Documentation/admin-guide/mm/pagemap.rst > @@ -78,6 +78,8 @@ number of times a page is mapped. > 23. BALLOON > 24. ZERO_PAGE > 25. IDLE > + 26. PGTABLE > + 27. OFFLINE So the offline *user* bit is new ... even though the *kernel* bit just renames the balloon bit. I'm not sure how I feel about this. I'm going to think about it some more. Could you share your decision process with us? I have no objection to renaming the balloon bit inside the kernel; I think that's a wise idea. I'm just not sure whether we should rename the user balloon bit rather than adding a new bit.