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=-12.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 EA016C48BC2 for ; Tue, 22 Jun 2021 00:04:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CA28660C41 for ; Tue, 22 Jun 2021 00:04:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230354AbhFVAGO (ORCPT ); Mon, 21 Jun 2021 20:06:14 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:41542 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229747AbhFVAGN (ORCPT ); Mon, 21 Jun 2021 20:06:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1624320238; h=from:from:reply-to: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qmPwelrhybYDdKxwzfvIvfEHDkXjrO7CGdG+GKdF17w=; b=hSKo6eiiqt3t6lZzRuhamqo6chQ8xP3Kbg+NathVLE7oqDJE3SvifTD8jdvYwRRd6uHs8K gKav36nBWprbpqqiTahK9HDBnQSsEiTwsqvA5laJLi0QeSXiIeo9EbsNdSCf4aCoOXKadd KZMCgy7G/2t7YS4OhCxdm8GbB9Kbvck= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-20-r6UKx4WZONyoWoP_k7hQqw-1; Mon, 21 Jun 2021 20:03:56 -0400 X-MC-Unique: r6UKx4WZONyoWoP_k7hQqw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5647E80734A; Tue, 22 Jun 2021 00:03:55 +0000 (UTC) Received: from [10.64.54.84] (vpn2-54-84.bne.redhat.com [10.64.54.84]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0E2C35C1C2; Tue, 22 Jun 2021 00:03:47 +0000 (UTC) Reply-To: Gavin Shan Subject: Re: ** POTENTIAL FRAUD ALERT - RED HAT ** RE: [PATCH 0/3] mm/page_reporting: Make page reporting work on arm64 with 64KB page size To: Michael Kelley , Alexander Duyck Cc: linux-mm , LKML , Andrew Morton , David Hildenbrand , Anshuman Khandual , Catalin Marinas , Will Deacon , "shan.gavin@gmail.com" References: <20210621051152.305224-1-gshan@redhat.com> From: Gavin Shan Message-ID: <2c0b0868-a972-2c04-a600-8333e0de2952@redhat.com> Date: Tue, 22 Jun 2021 12:04:49 +1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/22/21 2:06 AM, Michael Kelley wrote: > From: Alexander Duyck Sent: Monday, June 21, 2021 7:02 AM >> To: Gavin Shan >> Cc: linux-mm ; LKML ; Andrew >> Morton ; David Hildenbrand ; >> Anshuman Khandual ; Catalin Marinas >> ; Will Deacon ; shan.gavin@gmail.com >> Subject: Re: [PATCH 0/3] mm/page_reporting: Make page reporting work on arm64 with >> 64KB page size >> >> So the question I would have is what is the use case for this? It >> seems like you don't have to deal with the guest native page size >> issues since you are willing to break up what would otherwise be THP >> pages on the guest, and the fact that you are willing to go down to >> 2MB pages which happens to align with the host THP page size for x86 >> makes me wonder if that is actually the environment you are running >> in. >> >> Rather than having the guest control this it might make sense to look >> at adding an interface so that the page_reporting_register function >> and the page_reporting_dev_info struct could be used to report and >> configure the minimum page size that the host can support for the page >> reporting. With that the host could then guarantee that it isn't going >> to hurt performance by splitting pages on the host and risk hurting >> the virtualization performance. >> >> Also you would benefit by looking into the callers of >> page_reporting_register as there are more than just the virtio balloon >> that are consuming it. Odds are HyperV won't care about an ARM64 >> architecture, > > FWIW, Hyper-V *does* care about ARM64. It's already in use by > the Windows Subsystem for Linux VM that's part of Windows 10 > on ARM64 hardware. We're working to get the code accepted > upstream. > Michael, thanks for your confirmation. As the issue found on 64KB guest when memory balloon is used, lets resolve the case first. I will look into Hyper-V case later if you agree. It won't be difficult to fix the same issue for Hyper-V after the solution is figured out for memory balloon. Thanks, Gavin > >> but your change would essentially disable it outright >> which is why I think this might be better to address via the consumers >> of page reporting rather than trying to address it in page reporting >> itself. >> >> Thanks, >> >> - Alex >> >> On Sun, Jun 20, 2021 at 8:11 PM Gavin Shan wrote: >>> >>> The page reporting threshold is currently equal to @pageblock_order, which >>> is 13 and 512MB on arm64 with 64KB base page size selected. The page >>> reporting won't be triggered if the freeing page can't come up with a free >>> area like that huge. The condition is hard to be met, especially when the >>> system memory becomes fragmented. >>> >>> This series intends to solve the issue by having page reporting threshold >>> as 5 (2MB) on arm64 with 64KB base page size. The patches are organized as: >>> >>> PATCH[1/3] introduces variable (@page_reporting_order) to replace original >>> macro (PAGE_REPORTING_MIN_ORDER). It's also exported so that it >>> can be adjusted at runtime. >>> PATCH[2/3] renames PAGE_REPORTING_MIN_ORDER with PAGE_REPORTING_ORDER >> and >>> allows architecture to specify its own version. >>> PATCH[3/3] defines PAGE_REPORTING_ORDER to 5, corresponding to 2MB in size, >>> on arm64 when 64KB base page size is selected. It's still same >>> as to @pageblock_order for other architectures and cases. >>> >>> Gavin Shan (3): >>> mm/page_reporting: Allow to set reporting order >>> mm/page_reporting: Allow architecture to select reporting order >>> arm64: mm: Specify smaller page reporting order >>> >>> Documentation/admin-guide/kernel-parameters.txt | 6 ++++++ >>> arch/arm64/include/asm/page.h | 13 +++++++++++++ >>> mm/page_reporting.c | 8 ++++++-- >>> mm/page_reporting.h | 10 +++++++--- >>> 4 files changed, 32 insertions(+), 5 deletions(-) >>> >>> -- >>> 2.23.0 >>>