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=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 2AE62C433E0 for ; Tue, 12 Jan 2021 13:41:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D452F22285 for ; Tue, 12 Jan 2021 13:41:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727767AbhALNlk (ORCPT ); Tue, 12 Jan 2021 08:41:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54750 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726614AbhALNlj (ORCPT ); Tue, 12 Jan 2021 08:41:39 -0500 Received: from mail-pl1-x632.google.com (mail-pl1-x632.google.com [IPv6:2607:f8b0:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6E5A5C061575 for ; Tue, 12 Jan 2021 05:40:53 -0800 (PST) Received: by mail-pl1-x632.google.com with SMTP id y8so1408656plp.8 for ; Tue, 12 Jan 2021 05:40:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=zZLzXJhYGy3+C++xiu5/GWXfuaP9n5Tamv3Y6rIuM/8=; b=kOHEJUMIVd1E1RjqgU/ztHKBOTzyewT5NmxKsCh1MyIjNkQpn3ynCh447I7c+wigJD etc888HHTL5ebznnHgGueMOVDbMT40gwfn7zf1Rj0qlH3rZYbTUS0B9F81+cbdzIl8ZQ 012pn+8i0o5UYncK3n4aPa4tu/Raf/oO4yTkCJk8wSwHmcRwwJnaBg/LQKRt7YurwGqZ fjzLjWgYYry5eGhPEb5n1oVFZILi9NslRItFQYWLAc3g3BHziIWIzMZZmD8OkFMiQTN3 sTpipoSNX10cvyUbzpx64SqgZ7gxmscTdg+U/QtR05PtI4NDnm8nRDbHCVbcMEhabAd0 n4CQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=zZLzXJhYGy3+C++xiu5/GWXfuaP9n5Tamv3Y6rIuM/8=; b=Dcy0Aw40JZ7os0GcbqUKZPuOo9yodpg4wTxttdVKfuTAKukILzyaTNWGJqLOt7Peg/ U6AqcxVrEg03BELHh7Yjj0fxeiFhEXLITazqyWn2gYQtw5I9nLAb7OjfqdBVBC7Lqm7C HlWtmGnZk4MNC6ht+ymDQWF5Dg0aVGfyuOPzirnpjjh69BqwKOlRwcVejDp/4r/GGZR7 u0gDE0OzO0xDgCbFvR5FBL0/EjpsuGYzJciOKBDqHRqlBOTsZnhNcrSXeHYlrr16khjm MEWaVIrtQ0IRshO1AnTZhNCemZ6yxxY0RhelVMN5UDntLSBkq2OxT21/j+Kxw9C4FTZF Vzlg== X-Gm-Message-State: AOAM532wuxYvJskSm40taJgePsxISne5/TDNAXecpgZi78re+1EtA/Hc nH82l0ukEYLnXCJ3/FKlbzVDrFWeGMLinVzJwpgO3w== X-Google-Smtp-Source: ABdhPJwJEZGJ+XMYd1YH6xipHivHKF33qK778JtZmPGOLOYl8IQZuZfMXbQjQf/X6ZwG1AmN6AudjfgxIr54JVMOkRc= X-Received: by 2002:a17:90a:c588:: with SMTP id l8mr4678691pjt.147.1610458852955; Tue, 12 Jan 2021 05:40:52 -0800 (PST) MIME-Version: 1.0 References: <20210110124017.86750-1-songmuchun@bytedance.com> <20210110124017.86750-2-songmuchun@bytedance.com> <1b39d654-0b8c-de3a-55d1-6ab8c2b2e0ba@redhat.com> In-Reply-To: From: Muchun Song Date: Tue, 12 Jan 2021 21:40:07 +0800 Message-ID: Subject: Re: [External] Re: [PATCH v3 1/6] mm: migrate: do not migrate HugeTLB page whose refcount is one To: David Hildenbrand Cc: Mike Kravetz , Andrew Morton , Naoya Horiguchi , Andi Kleen , mhocko@suse.cz, Linux Memory Management List , LKML , Yang Shi Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 12, 2021 at 7:11 PM David Hildenbrand wrote: > > On 12.01.21 12:00, David Hildenbrand wrote: > > On 10.01.21 13:40, 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. > >> > >> This optimization is consistent with the regular pages, just like > >> unmap_and_move() does. > >> > >> Signed-off-by: Muchun Song > >> Reviewed-by: Mike Kravetz > >> Acked-by: Yang Shi > >> --- > >> 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; > >> > > > > Question: What if called via alloc_contig_range() where we even want to > > "migrate" free pages, meaning, relocate it? > > > > To be more precise: > > a) We don't have dissolve_free_huge_pages() calls on the > alloc_contig_range() path. So we *need* migration IIUC. Without this patch, if you want to migrate a HUgeTLB page, the page is freed to the hugepage pool. With this patch, the page is also freed to the hugepage pool. I didn't see any different. I am missing something? > > b) dissolve_free_huge_pages() will fail if going below the reservation. > In that case we really want to migrate free pages. This even applies to > memory offlining. > > Either I am missing something important or this patch is more dangerous > than it looks like. > > -- > Thanks, > > David / dhildenb > 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=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 AB218C433DB for ; Tue, 12 Jan 2021 13:40:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E168622B30 for ; Tue, 12 Jan 2021 13:40:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E168622B30 Authentication-Results: mail.kernel.org; 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c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=zZLzXJhYGy3+C++xiu5/GWXfuaP9n5Tamv3Y6rIuM/8=; b=FN1au1S7g0cJ9N3gXiHdka4s4RtcFL0su5cQLIEpiH3LUEZOGLHv9w1CSBmNTS2ccZ QTtEAnsk4oMuqV68zOWbDPyK1UpS+intGXXwTzRVNH52qVwo+AEKtMWWRbr8oLOqsUMr 6WrqYJRUCEENJbzm0fCX+PIoGL54mqzJ7F1d7L1LiJgfdEbo0aq1r59Ep6ggKiJlOucA r63P/Z5DpI3AcMWgdXlh46vaaYM+HXU2yneDZz26+FQDqg+UdyB1noclIgPW+vWsiGtR +f1IGTIHkN+aOz1OiZ+XlKVCu2yaWf35JO53D9eRShzk6HVbfOTvzsx1OsNiJB7Rt+KC s/Eg== X-Gm-Message-State: AOAM533G5KuNbUHC24IlY7y2l4oSU+11/9RY/jk5l0OhkDyA09KnI8aB QGsuEaZIVX89xRqbuaumKOSCTQsOda+T8/pS6d04DQ== X-Google-Smtp-Source: ABdhPJwJEZGJ+XMYd1YH6xipHivHKF33qK778JtZmPGOLOYl8IQZuZfMXbQjQf/X6ZwG1AmN6AudjfgxIr54JVMOkRc= X-Received: by 2002:a17:90a:c588:: with SMTP id l8mr4678691pjt.147.1610458852955; Tue, 12 Jan 2021 05:40:52 -0800 (PST) MIME-Version: 1.0 References: <20210110124017.86750-1-songmuchun@bytedance.com> <20210110124017.86750-2-songmuchun@bytedance.com> <1b39d654-0b8c-de3a-55d1-6ab8c2b2e0ba@redhat.com> In-Reply-To: From: Muchun Song Date: Tue, 12 Jan 2021 21:40:07 +0800 Message-ID: Subject: Re: [External] Re: [PATCH v3 1/6] mm: migrate: do not migrate HugeTLB page whose refcount is one To: David Hildenbrand Cc: Mike Kravetz , Andrew Morton , Naoya Horiguchi , Andi Kleen , mhocko@suse.cz, Linux Memory Management List , LKML , Yang Shi Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jan 12, 2021 at 7:11 PM David Hildenbrand wrote: > > On 12.01.21 12:00, David Hildenbrand wrote: > > On 10.01.21 13:40, 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. > >> > >> This optimization is consistent with the regular pages, just like > >> unmap_and_move() does. > >> > >> Signed-off-by: Muchun Song > >> Reviewed-by: Mike Kravetz > >> Acked-by: Yang Shi > >> --- > >> 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; > >> > > > > Question: What if called via alloc_contig_range() where we even want to > > "migrate" free pages, meaning, relocate it? > > > > To be more precise: > > a) We don't have dissolve_free_huge_pages() calls on the > alloc_contig_range() path. So we *need* migration IIUC. Without this patch, if you want to migrate a HUgeTLB page, the page is freed to the hugepage pool. With this patch, the page is also freed to the hugepage pool. I didn't see any different. I am missing something? > > b) dissolve_free_huge_pages() will fail if going below the reservation. > In that case we really want to migrate free pages. This even applies to > memory offlining. > > Either I am missing something important or this patch is more dangerous > than it looks like. > > -- > Thanks, > > David / dhildenb >