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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9B296C43334 for ; Mon, 11 Jul 2022 01:55:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229614AbiGKBzX (ORCPT ); Sun, 10 Jul 2022 21:55:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50986 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229469AbiGKBzV (ORCPT ); Sun, 10 Jul 2022 21:55:21 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D0A316428 for ; Sun, 10 Jul 2022 18:55:20 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Lh6My3bpyzhXYL; Mon, 11 Jul 2022 09:52:46 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 11 Jul 2022 09:55:17 +0800 Subject: Re: [mm-unstable PATCH v5 1/8] mm/hugetlb: check gigantic_page_runtime_supported() in return_unused_surplus_pages() To: Naoya Horiguchi , CC: Andrew Morton , David Hildenbrand , Mike Kravetz , Liu Shixin , Yang Shi , Oscar Salvador , Muchun Song , Naoya Horiguchi , References: <20220708053653.964464-1-naoya.horiguchi@linux.dev> <20220708053653.964464-2-naoya.horiguchi@linux.dev> From: Miaohe Lin Message-ID: Date: Mon, 11 Jul 2022 09:55:17 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20220708053653.964464-2-naoya.horiguchi@linux.dev> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/7/8 13:36, Naoya Horiguchi wrote: > From: Naoya Horiguchi > > I found a weird state of 1GB hugepage pool, caused by the following > procedure: > > - run a process reserving all free 1GB hugepages, > - shrink free 1GB hugepage pool to zero (i.e. writing 0 to > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages), then > - kill the reserving process. > > , then all the hugepages are free *and* surplus at the same time. > > $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages > 3 > $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/free_hugepages > 3 > $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/resv_hugepages > 0 > $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/surplus_hugepages > 3 > > This state is resolved by reserving and allocating the pages then > freeing them again, so this seems not to result in serious problem. > But it's a little surprising (shrinking pool suddenly fails). > > This behavior is caused by hstate_is_gigantic() check in > return_unused_surplus_pages(). This was introduced so long ago in 2008 > by commit aa888a74977a ("hugetlb: support larger than MAX_ORDER"), and > at that time the gigantic pages were not supposed to be allocated/freed > at run-time. Now kernel can support runtime allocation/free, so let's > check gigantic_page_runtime_supported() together. > > Signed-off-by: Naoya Horiguchi Looks good to me. Thanks. Reviewed-by: Miaohe Lin