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=-7.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 4B02AC433DB for ; Tue, 12 Jan 2021 14:42:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 093FE23121 for ; Tue, 12 Jan 2021 14:42:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730418AbhALOmh (ORCPT ); Tue, 12 Jan 2021 09:42:37 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:48777 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725984AbhALOmg (ORCPT ); Tue, 12 Jan 2021 09:42:36 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1610462470; 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=kJLhS6MrRmYcBy2q5fslcQ3ZrLD7BMqvtBIQ18v75Yw=; b=dsOKy89M+eeICuN4Eze+O7DH5bF/FxYkat+9UzzpfWViyPgIwx4b9XAuaBd0aK0dFMTcrZ LSjBrl2AnKK/km6U1RfMd29kF3tOcsi9aJX28RWcQt3G1rjSyFfuZmIC6R1GmMUL+Jl11V CfSMlMj6YgQad36Zn4TK+aKy67o6NgY= 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-3-b5tYlFyEN-6aTyXFKNVihA-1; Tue, 12 Jan 2021 09:41:06 -0500 X-MC-Unique: b5tYlFyEN-6aTyXFKNVihA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1584B802B46; Tue, 12 Jan 2021 14:41:05 +0000 (UTC) Received: from [10.36.115.140] (ovpn-115-140.ams2.redhat.com [10.36.115.140]) by smtp.corp.redhat.com (Postfix) with ESMTP id 202AC5B4B6; Tue, 12 Jan 2021 14:41:02 +0000 (UTC) Subject: Re: [PATCH v3 1/6] mm: migrate: do not migrate HugeTLB page whose refcount is one To: Michal Hocko Cc: Muchun Song , mike.kravetz@oracle.com, akpm@linux-foundation.org, n-horiguchi@ah.jp.nec.com, ak@linux.intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Yang Shi References: <20210110124017.86750-1-songmuchun@bytedance.com> <20210110124017.86750-2-songmuchun@bytedance.com> <1b39d654-0b8c-de3a-55d1-6ab8c2b2e0ba@redhat.com> <20210112112709.GO22493@dhcp22.suse.cz> <20210112121643.GP22493@dhcp22.suse.cz> <20210112142337.GR22493@dhcp22.suse.cz> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <52ec4899-80df-4cbe-41f1-e0a29e838afa@redhat.com> Date: Tue, 12 Jan 2021 15:41:02 +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: <20210112142337.GR22493@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12.01.21 15:23, Michal Hocko wrote: > On Tue 12-01-21 13:16:45, Michal Hocko wrote: > [...] >> Well, currently pool pages are not migrateable but you are right that >> this is likely something that we will need to look into in the future >> and this optimization would stand in the way. > > After some more thinking I believe I was wrong in my last statement. > This optimization shouldn't have any effect on pages on the pool as > those stay at reference count 0 and they cannot be isolated either > (clear_page_huge_active before it is enqueued). > > That being said, the migration code would still have to learn about > about this pages but that is out of scope of this discussion. > > Sorry about the confusion from my side. > At this point I am fairly confused what's working at what's not :D I think this will require more thought, on how to teach alloc_contig_range() (and eventually in some cases offline_pages()?) to do the right thing. -- Thanks, David / dhildenb