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 71165C43387 for ; Wed, 16 Jan 2019 12:30:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3AECB20578 for ; Wed, 16 Jan 2019 12:30:28 +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="lNphx2C7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392769AbfAPMa0 (ORCPT ); Wed, 16 Jan 2019 07:30:26 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:33784 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392477AbfAPMa0 (ORCPT ); Wed, 16 Jan 2019 07:30:26 -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-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender: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=hbXvLzXUjWRA8mvWs4q87Q48DPDygjGmEj0NoNFx3hs=; b=lNphx2C7jDquNNBJnKZgSUFRL dyHKgdNqqoc95W/4shDztc1/5Il66cPkk2DWcKaOfNeJYH4MnXwa8bN7zOjURxCTQZTZxdEWMjFu+ siyAKwPaIVUnX/t706vQrfNCnReNYSx7yItpfJsz6WkL296seVxXC3PNgroy3+XgeYzYQo6boq8cH rWnPSDEQMlDIxhO5rXQLJNqzPUknCi51kK9eZBpWw/iaCTNthz3cUJ7t7So1w4wf22fxlCRBIl4tI M8uAfnbr2pIJ83GDMRWAEN9I/rCOZcJ3pX8zwidYXe00X9AVyYO8Q+Dw4JRMtPAbxVNfvinWmzbwQ if5zfw4bA==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gjkKo-0003iy-9p; Wed, 16 Jan 2019 12:30:18 +0000 Date: Wed, 16 Jan 2019 04:30:18 -0800 From: Matthew Wilcox To: 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, mpe@ellerman.id.au, 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 Message-ID: <20190116123018.GF6310@bombadil.infradead.org> References: <1547619692-7946-1-git-send-email-anshuman.khandual@arm.com> <20190116065703.GE24149@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190116065703.GE24149@dhcp22.suse.cz> 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 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. Yet instead of spreading that goodness to all other architectures, Anshuman has gone to more effort to avoid doing that.