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 A7D97C433EF for ; Wed, 20 Apr 2022 06:17:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1357278AbiDTGUY (ORCPT ); Wed, 20 Apr 2022 02:20:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40398 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230473AbiDTGUW (ORCPT ); Wed, 20 Apr 2022 02:20:22 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BAA6F393E0 for ; Tue, 19 Apr 2022 23:17:37 -0700 (PDT) Received: from kwepemi100005.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Kjr4S6KlRzFpXF; Wed, 20 Apr 2022 14:15:04 +0800 (CST) Received: from kwepemm600017.china.huawei.com (7.193.23.234) by kwepemi100005.china.huawei.com (7.221.188.155) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 20 Apr 2022 14:17:35 +0800 Received: from [10.174.179.19] (10.174.179.19) by kwepemm600017.china.huawei.com (7.193.23.234) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 20 Apr 2022 14:17:34 +0800 Message-ID: Date: Wed, 20 Apr 2022 14:17:34 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.3.2 Subject: Re: [PATCH v4] hugetlb: Fix wrong use of nr_online_nodes Content-Language: en-US To: Kefeng Wang , Andrew Morton CC: , , , , , , , , References: <20220413032915.251254-2-liupeng256@huawei.com> <20220416103526.3287348-1-liupeng256@huawei.com> <20220418210352.1d1d90aeba477d598bd6f0be@linux-foundation.org> <4734132d-bae3-d3ab-33b3-a4c3282ad5cd@huawei.com> From: "liupeng (DM)" In-Reply-To: <4734132d-bae3-d3ab-33b3-a4c3282ad5cd@huawei.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.19] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemm600017.china.huawei.com (7.193.23.234) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/4/19 22:07, Kefeng Wang wrote: > > On 2022/4/19 12:03, Andrew Morton wrote: >> On Sat, 16 Apr 2022 10:35:26 +0000 Peng Liu >> wrote: >> >>> Certain systems are designed to have sparse/discontiguous nodes. In >>> this case, nr_online_nodes can not be used to walk through numa node. >>> Also, a valid node may be greater than nr_online_nodes. >>> >>> However, in hugetlb, it is assumed that nodes are contiguous. Recheck >>> all the places that use nr_online_nodes, and repair them one by one. >> oops. >> >> What are the user-visible runtime effects of this flaw? > > For example, there are four node=0,1,2,3, and nid = 1 is offline > node，nr_online_nodes = 3 > > 1) per-node alloc (hugepages=1:2) fails, > > 2) per-node alloc (hugepages=3:2) fails, but it could succeed. > > I assume that there is no user-visible runtime effects. > Thanks, you are right. I have constructed node =0, 1, 3, 4, and requested huge pages as: hugepagesz=1G hugepages=0:1,4:1 hugepagesz=2M hugepages=0:1024,4:1024 Without this patch:  HugeTLB: Invalid hugepages parameter 4:1  HugeTLB: Invalid hugepages parameter 4:1024  HugeTLB registered 1.00 GiB page size, pre-allocated 0 pages  HugeTLB registered 2.00 MiB page size, pre-allocated 1024 pages With this patch:   HugeTLB registered 1.00 GiB page size, pre-allocated 2 pages   HugeTLB registered 2.00 MiB page size, pre-allocated 2048 pages >> . > .