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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 B7CB4C43612 for ; Wed, 16 Jan 2019 14:20:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 864D1205C9 for ; Wed, 16 Jan 2019 14:20:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="umaZGSlS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404638AbfAPOUV (ORCPT ); Wed, 16 Jan 2019 09:20:21 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:57816 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2403767AbfAPOUU (ORCPT ); Wed, 16 Jan 2019 09:20:20 -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-Transfer-Encoding :Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To: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=SOzqtRQnhrzBV/2kqoR/jW1DTahkUHWwkEGG0EIDlt8=; b=umaZGSlS/Mx6cAOQCY2BhcS56F JTft6i3pABnXS+1yEzVxc6J/HnMUqGhP0z1/U/ELpC9SPiGJZcpycToje9yk1SCtTpJbuIjaAZfmP 9hgJTa4oK7erwr+7pkqsEdHsRPFYxHJAVeOHEDkR3daRz6oJ+hfPDRkmAFSHXgwkYW03JUr4iiiII pwe6c5cQNXDArfmTdHshCR5u/eyVvFEO+8x+kCLvbRtYRUabVSSELftUY6vgPIKuKwP7gszL4UsYi SgiqQeZoXMooGlZZ0v46pl3O6+uIH4DVqAg7COtrdlYJg5fVyENBSsXIpN1paT+qMmm9LyeLLhLV1 yd5Thhxg==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gjm3C-0006U0-M1; Wed, 16 Jan 2019 14:20:14 +0000 Date: Wed, 16 Jan 2019 06:20:14 -0800 From: Matthew Wilcox To: Christophe Leroy Cc: Anshuman Khandual , mark.rutland@arm.com, linux-sh@vger.kernel.org, peterz@infradead.org, catalin.marinas@arm.com, dave.hansen@linux.intel.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux@armlinux.org.uk, mingo@redhat.com, vbabka@suse.cz, rientjes@google.com, palmer@sifive.com, greentime@andestech.com, marc.zyngier@arm.com, rppt@linux.vnet.ibm.com, shakeelb@google.com, kirill@shutemov.name, tglx@linutronix.de, Michal Hocko , linux-arm-kernel@lists.infradead.org, ard.biesheuvel@linaro.org, robin.murphy@arm.com, steve.capper@arm.com, christoffer.dall@arm.com, james.morse@arm.com, aneesh.kumar@linux.ibm.com, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH V2] mm: Introduce GFP_PGTABLE Message-ID: <20190116142014.GJ6310@bombadil.infradead.org> References: <1547619692-7946-1-git-send-email-anshuman.khandual@arm.com> <20190116065703.GE24149@dhcp22.suse.cz> <20190116123018.GF6310@bombadil.infradead.org> <07d6a264-dccd-78ab-e8a9-2410bbef7b97@arm.com> <20190116131827.GH6310@bombadil.infradead.org> <521d8511-4c87-49c6-de03-67a71d5bacca@c-s.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <521d8511-4c87-49c6-de03-67a71d5bacca@c-s.fr> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 16, 2019 at 02:47:16PM +0100, Christophe Leroy wrote: > Le 16/01/2019 à 14:18, Matthew Wilcox a écrit : > > I disagree with your objective. Making more code common is a great idea, > > but this patch is too unambitious. We should be heading towards one or > > two page table allocation functions instead of having every architecture do > > its own thing. > > > > So start there. Move the x86 function into common code and convert one > > other architecture to use it too. > > Are we talking about pte_alloc_one_kernel() and pte_alloc_one() ? > > I'm not sure x86 function is the best common one, as it seems to allocate a > multiple of PAGE_SIZE only. And that's the common case. Most architectures use a single page for at least one level of the pte/pmd/pud/p4d/pgd hierarchy. Some use multiple pages and some use a fraction of a page. > Some arches like powerpc use pagetables which are smaller than a page, for > instance powerpc 8xx uses 4k pagetables even with 16k pages, which means a > single page can be used by 4 pagetables. Those can be added later. Note I said "one or two", and that's what I had in mind; I think we want one function that allocates just a page and another that allocates a page fragment. Then we can have a good discussion about what method we use; s390 and ppc use different techniques today and there's really no good reason for that.