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 X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3D6F1C433E6 for ; Sat, 13 Mar 2021 20:38:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E452B64EC4 for ; Sat, 13 Mar 2021 20:38:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234619AbhCMUha (ORCPT ); Sat, 13 Mar 2021 15:37:30 -0500 Received: from mail.kernel.org ([198.145.29.99]:36668 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234165AbhCMUg7 (ORCPT ); Sat, 13 Mar 2021 15:36:59 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id D578564ECD; Sat, 13 Mar 2021 20:36:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1615667819; bh=lrVRSwJF8M5etHaNGCsRwuMHeCP7ip37fuj2Mk8p21o=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=p/7UxP4+8dasaGAPa7pttK3E/8+FQ8ox9J+WxO7TOfSEWqYTugcp4mcpMevhQ+jis yGIe6zZaUUzVWcTnZdUOyT4W0s7eearabw+2GSU2dOxs+v93bvm9QByXDMFgVPCoiz O/Jh08ZOTkmesvom0o8j0BDmb6zvonJF+Wn6pCO8= Date: Sat, 13 Mar 2021 12:36:58 -0800 From: Andrew Morton To: "Matthew Wilcox (Oracle)" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v4 00/25] Page folios Message-Id: <20210313123658.ad2dcf79a113a8619c19c33b@linux-foundation.org> In-Reply-To: <20210305041901.2396498-1-willy@infradead.org> References: <20210305041901.2396498-1-willy@infradead.org> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 5 Mar 2021 04:18:36 +0000 "Matthew Wilcox (Oracle)" wrote: > Our type system does not currently distinguish between tail pages and > head or single pages. This is a problem because we call compound_head() > multiple times (and the compiler cannot optimise it out), bloating the > kernel. It also makes programming hard as it is often unclear whether > a function operates on an individual page, or an entire compound page. > > This patch series introduces the struct folio, which is a type that > represents an entire compound page. This initial set reduces the kernel > size by approximately 6kB, although its real purpose is adding > infrastructure to enable further use of the folio. Geeze it's a lot of noise. More things to remember and we'll forever have a mismash of `page' and `folio' and code everywhere converting from one to the other. Ongoing addition of folio accessors/manipulators to overlay the existing page accessors/manipulators, etc. It's unclear to me that it's all really worth it. What feedback have you seen from others?