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=-2.1 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 DF24FC6786E for ; Fri, 26 Oct 2018 08:55:50 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 12D6C20834 for ; Fri, 26 Oct 2018 08:55:49 +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="ucA2s1NE" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 12D6C20834 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 42hHrz3fdHzF3GT for ; Fri, 26 Oct 2018 19:55:47 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=infradead.org header.i=@infradead.org header.b="ucA2s1NE"; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=none (mailfrom) smtp.mailfrom=infradead.org (client-ip=2001:8b0:10b:1231::1; helo=merlin.infradead.org; envelope-from=peterz@infradead.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=infradead.org Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 42hHp16ljJzF3GH for ; Fri, 26 Oct 2018 19:53:09 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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=pbk9Jp4NpLV5KhCv2GieE6eo6VugTGuTfEvdAP/DTOU=; b=ucA2s1NEduQA2HG6o8PHl9GX1 1c9iAfHE+3hqIl/VOcrEC4U61PEkSMe2UlNY8ypIaHjQM2VFqPCLJW1X9TyB3wWuCgKbVPigZk0cL 8xXH3vrCr+QLGW8A+8M1aJInEB7Ent4aKqtrYwIq3zSx2xpx4WErOiYwf+CUPAYBaTROX2LN6wtam SO+PDPDdJ9gkMza75ER7YzuuEE9Nbr1grRJK7p7fXgBxca+Uj29aAUjQiybM8sVWM4X51T4/vAu3t jGJE+MJ5H5/n+ZlZg0mYiuiT+wrbdPBImX4VY03B6CnjBGen3lPKGeN206IfOOZzbJStVnZtSqh8h j/PfTfURA==; Received: from [167.98.65.38] (helo=worktop) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gFxqe-000103-2S; Fri, 26 Oct 2018 08:52:04 +0000 Received: by worktop (Postfix, from userid 1000) id A96EE6E07CA; Fri, 26 Oct 2018 10:52:02 +0200 (CEST) Date: Fri, 26 Oct 2018 10:52:02 +0200 From: Peter Zijlstra To: Joel Fernandes Subject: Re: [PATCH 1/4] treewide: remove unused address argument from pte_alloc functions (v2) Message-ID: <20181026085202.GC3109@worktop.c.hoisthospitality.com> References: <20181013013200.206928-1-joel@joelfernandes.org> <20181013013200.206928-2-joel@joelfernandes.org> <20181024083716.GN3109@worktop.c.hoisthospitality.com> <20181025022119.GC13560@joelaf.mtv.corp.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181025022119.GC13560@joelaf.mtv.corp.google.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-mips@linux-mips.org, Rich Felker , linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Catalin Marinas , Dave Hansen , Will Deacon , Michal Hocko , linux-mm@kvack.org, lokeshgidra@google.com, sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org, elfring@users.sourceforge.net, Jonas Bonn , kvmarm@lists.cs.columbia.edu, dancol@google.com, Yoshinori Sato , linux-xtensa@linux-xtensa.org, linux-hexagon@vger.kernel.org, Helge Deller , "maintainer:X86 ARCHITECTURE \(32-BIT AND 64-BIT\)" , hughd@google.com, "James E.J. Bottomley" , kasan-dev@googlegroups.com, anton.ivanov@kot-begemot.co.uk, Ingo Molnar , Geert Uytterhoeven , Andrey Ryabinin , linux-snps-arc@lists.infradead.org, kernel-team@android.com, Sam Creasey , Fenghua Yu , linux-s390@vger.kernel.org, Jeff Dike , linux-um@lists.infradead.org, Stefan Kristiansson , Julia Lawall , linux-m68k@lists.linux-m68k.org, Borislav Petkov , Andy Lutomirski , nios2-dev@lists.rocketboards.org, "Kirill A . Shutemov" , Stafford Horne , Guan Xuetao , Chris Zankel , Tony Luck , Richard Weinberger , linux-parisc@vger.kernel.org, Max Filippov , pantin@google.com, linux-kernel@vger.kernel.org, minchan@kernel.org, Thomas Gleixner , linux-alpha@vger.kernel.org, Ley Foon Tan , akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, "David S. Miller" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Oct 24, 2018 at 07:21:19PM -0700, Joel Fernandes wrote: > On Wed, Oct 24, 2018 at 10:37:16AM +0200, Peter Zijlstra wrote: > > On Fri, Oct 12, 2018 at 06:31:57PM -0700, Joel Fernandes (Google) wrote: > > > This series speeds up mremap(2) syscall by copying page tables at the > > > PMD level even for non-THP systems. There is concern that the extra > > > 'address' argument that mremap passes to pte_alloc may do something > > > subtle architecture related in the future that may make the scheme not > > > work. Also we find that there is no point in passing the 'address' to > > > pte_alloc since its unused. So this patch therefore removes this > > > argument tree-wide resulting in a nice negative diff as well. Also > > > ensuring along the way that the enabled architectures do not do anything > > > funky with 'address' argument that goes unnoticed by the optimization. > > > > Did you happen to look at the history of where that address argument > > came from? -- just being curious here. ISTR something vague about > > architectures having different paging structure for different memory > > ranges. > > I didn't happen to do that analysis but from code analysis, no architecutre > is using it. Since its unused in the kernel, may be such architectures don't > exist or were removed, so we don't need to bother? Could you share more about > your concern with the removal of this argument? No concerns at all with removing it; I was purely curious as to the origin of the unused argument. Kirill provided that answer.