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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,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 7EA6FC3A5A5 for ; Tue, 3 Sep 2019 06:19:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5CAA9215EA for ; Tue, 3 Sep 2019 06:19:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726986AbfICGTx (ORCPT ); Tue, 3 Sep 2019 02:19:53 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:6183 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726980AbfICGTx (ORCPT ); Tue, 3 Sep 2019 02:19:53 -0400 Received: from DGGEMS412-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 3346C78A70894A92193E; Tue, 3 Sep 2019 14:19:48 +0800 (CST) Received: from [127.0.0.1] (10.74.191.121) by DGGEMS412-HUB.china.huawei.com (10.3.19.212) with Microsoft SMTP Server id 14.3.439.0; Tue, 3 Sep 2019 14:19:41 +0800 Subject: Re: [PATCH v2 2/9] x86: numa: check the node id consistently for x86 To: Peter Zijlstra CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Greg Kroah-Hartman , "Rafael J. Wysocki" References: <1567231103-13237-1-git-send-email-linyunsheng@huawei.com> <1567231103-13237-3-git-send-email-linyunsheng@huawei.com> <20190831085539.GG2369@hirez.programming.kicks-ass.net> <4d89c688-49e4-a2aa-32ee-65e36edcd913@huawei.com> <20190831161247.GM2369@hirez.programming.kicks-ass.net> <20190902072542.GN2369@hirez.programming.kicks-ass.net> <5fa2aa99-89fa-cd41-b090-36a23cfdeb73@huawei.com> <20190902125644.GQ2369@hirez.programming.kicks-ass.net> From: Yunsheng Lin Message-ID: <1f48081c-c9d6-8f3e-9559-8b0bec98f125@huawei.com> Date: Tue, 3 Sep 2019 14:19:04 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20190902125644.GQ2369@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.74.191.121] X-CFilter-Loop: Reflected Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On 2019/9/2 20:56, Peter Zijlstra wrote: > On Mon, Sep 02, 2019 at 08:25:24PM +0800, Yunsheng Lin wrote: >> On 2019/9/2 15:25, Peter Zijlstra wrote: >>> On Mon, Sep 02, 2019 at 01:46:51PM +0800, Yunsheng Lin wrote: >>>> On 2019/9/1 0:12, Peter Zijlstra wrote: >>> >>>>> 1) because even it is not set, the device really does belong to a node. >>>>> It is impossible a device will have magic uniform access to memory when >>>>> CPUs cannot. >>>> >>>> So it means dev_to_node() will return either NUMA_NO_NODE or a >>>> valid node id? >>> >>> NUMA_NO_NODE := -1, which is not a valid node number. It is also, like I >>> said, not a valid device location on a NUMA system. >>> >>> Just because ACPI/BIOS is shit, doesn't mean the device doesn't have a >>> node association. It just means we don't know and might have to guess. >> >> How do we guess the device's location when ACPI/BIOS does not set it? > > See device_add(), it looks to the device's parent and on NO_NODE, puts > it there. > > Lacking any hints, just stick it to node0 and print a FW_BUG or > something. > >> It seems dev_to_node() does not do anything about that and leave the >> job to the caller or whatever function that get called with its return >> value, such as cpumask_of_node(). > > Well, dev_to_node() doesn't do anything; nor should it. It are the > callers of set_dev_node() that should be taking care. > > Also note how device_add() sets the device node to the parent device's > node on NUMA_NO_NODE. Arguably we should change it to complain when it > finds NUMA_NO_NODE and !parent. Is it possible that the node id set by device_add() become invalid if the node is offlined, then dev_to_node() may return a invalid node id. >From the comment in select_fallback_rq(), it seems that a node can be offlined, not sure if node offline process has taken cared of that? /* * If the node that the CPU is on has been offlined, cpu_to_node() * will return -1. There is no CPU on the node, and we should * select the CPU on the other node. */ With the above assumption that a device is always on a valid node, the node id returned from dev_to_node() can be safely passed to cpumask_of_node() without any checking? > > --- > drivers/base/core.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/drivers/base/core.c b/drivers/base/core.c > index f0dd8e38fee3..2caf204966a0 100644 > --- a/drivers/base/core.c > +++ b/drivers/base/core.c > @@ -2120,8 +2120,16 @@ int device_add(struct device *dev) > dev->kobj.parent = kobj; > > /* use parent numa_node */ > - if (parent && (dev_to_node(dev) == NUMA_NO_NODE)) > - set_dev_node(dev, dev_to_node(parent)); > + if (dev_to_node(dev) == NUMA_NO_NODE) { > + if (parent) > + set_dev_node(dev, dev_to_node(parent)); > +#ifdef CONFIG_NUMA > + else { > + pr_err("device: '%s': has no assigned NUMA node\n", dev_name(dev)); > + set_dev_node(dev, 0); > + } > +#endif > + } > > /* first, register with generic layer. */ > /* we require the name to be set before, and pass NULL */ > > . >