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=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,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 9023CC48BE5 for ; Tue, 22 Jun 2021 22:52:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6C6ED61107 for ; Tue, 22 Jun 2021 22:52:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230518AbhFVWyn (ORCPT ); Tue, 22 Jun 2021 18:54:43 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:46036 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229800AbhFVWym (ORCPT ); Tue, 22 Jun 2021 18:54:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1624402345; 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=ZAToiYSoBX48PZwkBHA5eLSjXvs8urxlIWQJRJqGGyU=; b=D+YhuLVLe+RyW/h1Zwutqai0Zw37rTl309d68dr/UiDWI6SavoEOTlbfJloCT6A/9VF90f 1jUVZsRa0tJzgUukVtvEsnvWRJwR0sNCRWqpNKpcq2v7lVNvCwxZoq+Cuq6myOP28VdDqu GOaAJjk+gJIIjBI1NYRO3ywsGYtkX0w= 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-583-T05E8pI-NBK_8d_Mp3dRug-1; Tue, 22 Jun 2021 18:52:21 -0400 X-MC-Unique: T05E8pI-NBK_8d_Mp3dRug-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2B9A7108A78D; Tue, 22 Jun 2021 22:46:39 +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 2F20B19C66; Tue, 22 Jun 2021 22:46:28 +0000 (UTC) Reply-To: Gavin Shan Subject: Re: [PATCH v2 3/3] virtio_balloon: Specify page reporting order if needed To: Alexander Duyck Cc: linux-mm , LKML , David Hildenbrand , "Michael S. Tsirkin" , Andrew Morton , Anshuman Khandual , Catalin Marinas , Will Deacon , shan.gavin@gmail.com References: <20210622074926.333223-1-gshan@redhat.com> <20210622074926.333223-4-gshan@redhat.com> From: Gavin Shan Message-ID: <3e449606-e02f-7c09-45e3-8d2401b53086@redhat.com> Date: Wed, 23 Jun 2021 10:47:30 +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 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/23/21 3:44 AM, Alexander Duyck wrote: > On Mon, Jun 21, 2021 at 10:49 PM Gavin Shan wrote: >> >> The page reporting won't be triggered if the freeing page can't come >> up with a free area, whose size is equal or bigger than the threshold >> (page reporting order). The default page reporting order, equal to >> @pageblock_order, is too huge on some architectures to trigger page >> reporting. One example is ARM64 when 64KB base page size is used. >> >> PAGE_SIZE: 64KB >> pageblock_order: 13 (512MB) >> MAX_ORDER: 14 >> >> This specifies the page reporting order to 5 (2MB) for this specific >> case so that page reporting can be triggered. >> >> Cc: Michael S. Tsirkin >> Cc: David Hildenbrand >> Cc: virtualization@lists.linux-foundation.org >> Signed-off-by: Gavin Shan >> --- >> drivers/virtio/virtio_balloon.c | 17 +++++++++++++++++ >> 1 file changed, 17 insertions(+) >> >> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c >> index 510e9318854d..fd419780cc23 100644 >> --- a/drivers/virtio/virtio_balloon.c >> +++ b/drivers/virtio/virtio_balloon.c >> @@ -993,6 +993,23 @@ static int virtballoon_probe(struct virtio_device *vdev) >> goto out_unregister_oom; >> } >> >> + /* >> + * The default page reporting order is @pageblock_order, which >> + * corresponds to 512MB in size on ARM64 when 64KB base page >> + * size is used. The page reporting won't be triggered if the >> + * freeing page can't come up with a free area like that huge. >> + * So we specify the page reporting order to 5, corresponding >> + * to 2MB. It helps to avoid THP splitting if 4KB base page >> + * size is used by host. >> + * >> + * Ideallh, the page reporting order is selected based on the > > "Ideally" > Yeah, I noticed it right after the patch was posted. Will be fixed in v3. >> + * host's base page size. However, it needs more work to report >> + * that value. The hardcoded order would be fine currently. >> + */ >> +#if defined(CONFIG_ARM64) && defined(CONFIG_ARM64_64K_PAGES) >> + vb->pr_dev_info.order = 5; >> +#endif >> + >> err = page_reporting_register(&vb->pr_dev_info); >> if (err) >> goto out_unregister_oom; > > This works for now. However my preference would be to look into seeing > if we can add a value that the host can report that would override the > value you selected here. Then in situations where the host has a > smaller THP page size then the guest it can report the preferred > reporting order via the virtio_balloon interface and have greater > flexibility. > > Reviewed-by: Alexander Duyck > Yes, It's something for later. Lets fix the particular case (ARM64 and 64KB page size) for now. Thanks, Gavin