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=-17.8 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,USER_AGENT_SANE_1 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 610F3C433DB for ; Tue, 5 Jan 2021 18:07:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 103D622D06 for ; Tue, 5 Jan 2021 18:07:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730762AbhAESGt (ORCPT ); Tue, 5 Jan 2021 13:06:49 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:51361 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730743AbhAESGr (ORCPT ); Tue, 5 Jan 2021 13:06:47 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1609869920; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=UESOViXeUqqgxTdJOAvu5P6aSrx26z1BgEX3o3McZLI=; b=gK+EbbmoXYwl0CHUhBOylcDh+3rzbaCuvnZRg0d1qhkEeG+VgWaVxpYSt3A1NQjgv96nLt am5CoOraNs2OZ+QKvXOHDT/dr92FMnsECaHlH9deUO2EElrxu+st7mknHZ9xkEwnAkFGZO x0pBhPgPyNusRsOKyF/tusGvNACb1YY= 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-365-wVG8_QOEOE2lzpYxfpzJkw-1; Tue, 05 Jan 2021 13:05:18 -0500 X-MC-Unique: wVG8_QOEOE2lzpYxfpzJkw-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 5B4A984A5E0; Tue, 5 Jan 2021 18:05:16 +0000 (UTC) Received: from [10.36.114.117] (ovpn-114-117.ams2.redhat.com [10.36.114.117]) by smtp.corp.redhat.com (Postfix) with ESMTP id C1A5D1F46F; Tue, 5 Jan 2021 18:05:13 +0000 (UTC) Subject: Re: [PATCH 1/6] mm: migrate: do not migrate HugeTLB page whose refcount is one To: Yang Shi Cc: Muchun Song , Mike Kravetz , Andrew Morton , hillf.zj@alibaba-inc.com, Naoya Horiguchi , ak@linux.intel.com, yongjun_wei@trendmicro.com.cn, mhocko@suse.cz, Linux MM , Linux Kernel Mailing List References: <20210104065843.5658-1-songmuchun@bytedance.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: Date: Tue, 5 Jan 2021 19:05:12 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 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 05.01.21 19:04, Yang Shi wrote: > On Tue, Jan 5, 2021 at 8:58 AM David Hildenbrand wrote: >> >> On 04.01.21 07:58, Muchun Song wrote: >>> If the refcount is one when it is migrated, it means that the page >>> was freed from under us. So we are done and do not need to migrate. >>> >>> Signed-off-by: Muchun Song >>> --- >>> mm/migrate.c | 6 ++++++ >>> 1 file changed, 6 insertions(+) >>> >>> diff --git a/mm/migrate.c b/mm/migrate.c >>> index 4385f2fb5d18..a6631c4eb6a6 100644 >>> --- a/mm/migrate.c >>> +++ b/mm/migrate.c >>> @@ -1279,6 +1279,12 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, >>> return -ENOSYS; >>> } >>> >>> + if (page_count(hpage) == 1) { >>> + /* page was freed from under us. So we are done. */ >>> + putback_active_hugepage(hpage); >>> + return MIGRATEPAGE_SUCCESS; >>> + } >>> + >>> new_hpage = get_new_page(hpage, private); >>> if (!new_hpage) >>> return -ENOMEM; >>> >> >> This series seems to fix quite some important cases (thanks). Do we want >> to cc stable some/all? > > For this particular one, I don't think so IMHO. It is an optimization > rather than a bug fix. I'm rather referring to the actual fixes (I received no cover letter so I picked the first patch in the series) -- Thanks, David / dhildenb