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 CBEA2C433EF for ; Mon, 4 Jul 2022 04:32:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231584AbiGDEcu (ORCPT ); Mon, 4 Jul 2022 00:32:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50222 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229461AbiGDEcs (ORCPT ); Mon, 4 Jul 2022 00:32:48 -0400 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:32c8:5054:ff:fe00:142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8B1BA55B2 for ; Sun, 3 Jul 2022 21:32:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: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=YYKbXvB/b/OIVTpzpeh7Y3tTbzRBSh+cFFhkPT74VhM=; b=kGJGgWeKv+2p7fAR+7kqPMnGZO 4kyvqm6bWq+iYc0ZZxH8sVhRcIOXkj5ECpkMpXhj0ZDtpGQ5Ja6Y86MIQOiTvQ62ugNmGHzNAqE+b XTUAc7mjs8xdlunUZG4/zhXv8LDJXZ0A+ex/+1KJaiPBSK25Vx+2MrMI1fB+snkKknCSxjIyYyMkU M5AP2AECWelxZo8oCYVuMfKBy6ewJxe9/JBTOSLz5a5UulWc+XqspUP9nTru3rSOeCITiHYCeJma2 924vw+V1F4fTfts1DsaSY1iEMT9/G8tZUKSLFQhEAB8hdJH5jKSX7R9O69hKLSbWod2Hc3XWRRT56 eHDmZwxw==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:33156) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1o8DlE-0007tN-NS; Mon, 04 Jul 2022 05:32:36 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.94.2) (envelope-from ) id 1o8DlB-0001r8-97; Mon, 04 Jul 2022 05:32:33 +0100 Date: Mon, 4 Jul 2022 05:32:33 +0100 From: "Russell King (Oracle)" To: Matthew Wilcox 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: Sender: Russell King (Oracle) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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" ? "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!