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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 381B9C43387 for ; Thu, 17 Jan 2019 09:56:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0ECC420657 for ; Thu, 17 Jan 2019 09:56:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727213AbfAQJ4n (ORCPT ); Thu, 17 Jan 2019 04:56:43 -0500 Received: from ozlabs.org ([203.11.71.1]:48615 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727201AbfAQJ4m (ORCPT ); Thu, 17 Jan 2019 04:56:42 -0500 Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPSA id 43gKGp5Rwwz9sBn; Thu, 17 Jan 2019 20:56:34 +1100 (AEDT) From: Michael Ellerman To: Matthew Wilcox , Michal Hocko Cc: Anshuman Khandual , linux-mm@kvack.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-sh@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-riscv@lists.infradead.org, linux@armlinux.org.uk, catalin.marinas@arm.com, will.deacon@arm.com, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, peterz@infradead.org, christoffer.dall@arm.com, marc.zyngier@arm.com, kirill@shutemov.name, rppt@linux.vnet.ibm.com, ard.biesheuvel@linaro.org, mark.rutland@arm.com, steve.capper@arm.com, james.morse@arm.com, robin.murphy@arm.com, aneesh.kumar@linux.ibm.com, vbabka@suse.cz, shakeelb@google.com, rientjes@google.com, palmer@sifive.com, greentime@andestech.com Subject: Re: [PATCH V2] mm: Introduce GFP_PGTABLE In-Reply-To: <20190116123018.GF6310@bombadil.infradead.org> References: <1547619692-7946-1-git-send-email-anshuman.khandual@arm.com> <20190116065703.GE24149@dhcp22.suse.cz> <20190116123018.GF6310@bombadil.infradead.org> Date: Thu, 17 Jan 2019 20:56:34 +1100 Message-ID: <87tvi74nfx.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Matthew Wilcox writes: > On Wed, Jan 16, 2019 at 07:57:03AM +0100, Michal Hocko wrote: >> On Wed 16-01-19 11:51:32, Anshuman Khandual wrote: >> > All architectures have been defining their own PGALLOC_GFP as (GFP_KERNEL | >> > __GFP_ZERO) and using it for allocating page table pages. This causes some >> > code duplication which can be easily avoided. GFP_KERNEL allocated and >> > cleared out pages (__GFP_ZERO) are required for page tables on any given >> > architecture. This creates a new generic GFP flag flag which can be used >> > for any page table page allocation. Does not cause any functional change. >> > >> > GFP_PGTABLE is being added into include/asm-generic/pgtable.h which is the >> > generic page tabe header just to prevent it's potential misuse as a general >> > allocation flag if included in include/linux/gfp.h. >> >> I haven't reviewed the patch yet but I am wondering whether this is >> really worth it without going all the way down to unify the common code >> and remove much more code duplication. Or is this not possible for some >> reason? > > Exactly what I suggested doing in response to v1. > > Also, the approach taken here is crazy. x86 has a feature that no other > architecture has bothered to implement yet -- accounting page tables > to the process. powerpc does __GFP_ACCOUNT for user page tables too. Shamelessly cribbed from the x86 version of course :) cheers