From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0C21AC43334 for ; Mon, 4 Jul 2022 10:48:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233440AbiGDKs4 (ORCPT ); Mon, 4 Jul 2022 06:48:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43110 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233443AbiGDKsu (ORCPT ); Mon, 4 Jul 2022 06:48:50 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 76B68DEE4 for ; Mon, 4 Jul 2022 03:48:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=R065WUthmqEzgKWBrKAm5cYHdmg6DG4yvVjf9aretus=; b=vIRAshX83ml6lhx5YzTLRFSdLx +/XlOOmPWFLIb8vohBG+auYtcUzx49+jp/UVKIKc1b+q+4TRRpi9MFRJpCp8ebYN0Et8QZHy7LUoH v1hXcq2aLAEcKEHtFD9x9Ef5CHAVH2Q/xVa6xKiTnDjCgzkZzLwcDj/HHblGh7e9Zzd3w9H59yu7V 1g0If6WEv5JgyNbKNzfX/x5SJQ9Rw4eIwxjLa2zd7f3ryUfy/bm79K7eJfrnNg8MT58BGR8t7eQO1 3YUW94KTxi/q/QYCE8C29s4V4ewUg75zmGTi7n0WCD3iTO3AnDRRcsG1rEyPkClQqvEvCvbxMvR77 ty9vwmUQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1o8Jd9-00HBz8-Pt; Mon, 04 Jul 2022 10:48:39 +0000 Date: Mon, 4 Jul 2022 11:48:39 +0100 From: Matthew Wilcox To: "Russell King (Oracle)" Cc: Andrew Morton , Arnd Bergmann , Mike Rapoport , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 15/14] arm: Rename PMD_ORDER to PMD_BITS Message-ID: References: <20220703141203.147893-1-rppt@kernel.org> <20220703211441.3981873-1-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 04, 2022 at 05:32:33AM +0100, Russell King (Oracle) wrote: > On Sun, Jul 03, 2022 at 10:54:49PM +0100, Matthew Wilcox wrote: > > On Sun, Jul 03, 2022 at 10:16:45PM +0100, Russell King (Oracle) wrote: > > > On Sun, Jul 03, 2022 at 10:14:41PM +0100, Matthew Wilcox (Oracle) wrote: > > > > This is the number of bits used by a PMD entry, not the order of a PMD. > > > > > > No, it's not the number of bits. A PMD entry doesn't fit in 2 or 3 bits. > > > This is even more confusing. > > > > Well, what is it then? The order of something is PAGE_SIZE << n, and > > that doesn't seem to be what this is. > > Where is it defined that "order" means "PAGE_SIZE << n" ? include/asm-generic/getorder.h: * get_order - Determine the allocation order of a memory size > "order" here is "order of magnitude" and in this case, it is 2^n, just > like order of magnitude in base 10 is 10^n. So strictly, the usage > here is completely correct, but if you describe "order" as "PAGE_SIZE << > n" that is no longer an order of magnitude, because it doesn't increase > in an order of magnitude (iow, n = 2 isn't PAGE_SIZE * PAGE_SIZE). > > Now, if you're trying to tell me that Linux has decided to define > "order" to be something non-standard, I'll accept that, but then we > shouldn't be renaming stuff that is using it in a standard way. > > -- > RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ > FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!