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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, 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 C519CC433DF for ; Fri, 16 Oct 2020 18:21:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 27320208E4 for ; Fri, 16 Oct 2020 18:21:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="MfcdBprO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391549AbgJPSVv (ORCPT ); Fri, 16 Oct 2020 14:21:51 -0400 Received: from mail.skyhub.de ([5.9.137.197]:32892 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391545AbgJPSVv (ORCPT ); Fri, 16 Oct 2020 14:21:51 -0400 Received: from zn.tnic (p200300ec2f0d0d00cf555b949331184a.dip0.t-ipconnect.de [IPv6:2003:ec:2f0d:d00:cf55:5b94:9331:184a]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 15C821EC0502; Fri, 16 Oct 2020 20:21:50 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1602872510; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=YUQjk3PEP/Lxo9pK9C44oGWzEABQvzmK7tR90OE3q3A=; b=MfcdBprO82Gs6USW3t2uxtDnPe1JyUvB0k99HSBCcmVqvcLThIJkxEdkmwMpSfYDH5N1kP MrZXJ2BALq3J8u5gh7xlv9mJuZqSpLP0lRjVkOhhDoM60RM5sdUx68Y9dfuw+VRziFrW/J goMyW63H1+aGXJPvshIJoTJqgJoiyrI= Date: Fri, 16 Oct 2020 20:21:40 +0200 From: Borislav Petkov To: Ankur Arora Cc: Andy Lutomirski , Andy Lutomirski , LKML , Linux-MM , "Kirill A. Shutemov" , Michal Hocko , Boris Ostrovsky , Konrad Rzeszutek Wilk , Thomas Gleixner , Ingo Molnar , X86 ML , "H. Peter Anvin" , Arnd Bergmann , Andrew Morton , Ira Weiny , linux-arch Subject: Re: [PATCH 5/8] x86/clear_page: add clear_page_uncached() Message-ID: <20201016182140.GJ8483@zn.tnic> References: <20201014195823.GC18196@zn.tnic> <22E29783-F1F5-43DA-B35F-D75FB247475D@amacapital.net> <20201014211214.GD18196@zn.tnic> <3de58840-1f4c-566b-3a66-46d57475820c@oracle.com> <20201015103535.GC11838@zn.tnic> <593f3b75-678c-1cd4-a7f0-55257dc84caf@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <593f3b75-678c-1cd4-a7f0-55257dc84caf@oracle.com> Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Thu, Oct 15, 2020 at 02:20:36PM -0700, Ankur Arora wrote: > The case I was thinking of was that clear_huge_page() That loop in clear_gigantic_page() there could be optimized not to iterate over the pages but do a NTA moves in one go, provided they're contiguous. > or faultin_page() would faultin_page() goes into the bowels of mm fault handling, you'd have to be more precise what exactly you mean with that one. > know the size to a page unit, while the higher level function would know the > whole extent and could optimize differently based on that. Just don't forget that this "optimization" of yours comes at the price of added code complexity and you're putting the onus on the people to know which function to call. So it is not for free and needs to be carefully weighed. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette