From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753165AbcEWHDL (ORCPT <rfc822;w@1wt.eu>);
	Mon, 23 May 2016 03:03:11 -0400
Received: from cn.fujitsu.com ([59.151.112.132]:33451 "EHLO
	heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org
	with ESMTP id S1753033AbcEWHDJ (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 23 May 2016 03:03:09 -0400
X-IronPort-AV: E=Sophos;i="5.22,518,1449504000"; 
   d="scan'208";a="6799077"
Message-ID: <5742AAF6.3060901@cn.fujitsu.com>
Date: Mon, 23 May 2016 15:02:14 +0800
From: Zhu Guihua <zhugh.fnst@cn.fujitsu.com>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0
MIME-Version: 1.0
To: Peter Zijlstra <peterz@infradead.org>
CC: <cl@linux.com>, <tj@kernel.org>, <mika.j.penttila@gmail.com>,
        <mingo@redhat.com>, <akpm@linux-foundation.org>, <rjw@rjwysocki.net>,
        <hpa@zytor.com>, <yasu.isimatu@gmail.com>,
        <isimatu.yasuaki@jp.fujitsu.com>, <kamezawa.hiroyu@jp.fujitsu.com>,
        <izumi.taku@jp.fujitsu.com>, <gongzhaogang@inspur.com>,
        <len.brown@intel.com>, <lenb@kernel.org>, <tglx@linutronix.de>,
        <chen.tang@easystack.cn>, <rafael@kernel.org>, <x86@kernel.org>,
        <linux-acpi@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-mm@kvack.org>
Subject: Re: [PATCH v7 0/5] Make cpuid <-> nodeid mapping persistent
References: <cover.1463652944.git.zhugh.fnst@cn.fujitsu.com> <20160519144657.GK3206@twins.programming.kicks-ass.net>
In-Reply-To: <20160519144657.GK3206@twins.programming.kicks-ass.net>
Content-Type: text/plain; charset="windows-1252"; format=flowed
Content-Transfer-Encoding: 7bit
X-Originating-IP: [10.167.226.252]
X-yoursite-MailScanner-ID: 875C442B66E2.AD9D3
X-yoursite-MailScanner: Found to be clean
X-yoursite-MailScanner-From: zhugh.fnst@cn.fujitsu.com
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi,

On 05/19/2016 10:46 PM, Peter Zijlstra wrote:
> On Thu, May 19, 2016 at 06:39:41PM +0800, Zhu Guihua wrote:
>> [Problem]
>>
>> cpuid <-> nodeid mapping is firstly established at boot time. And workqueue caches
>> the mapping in wq_numa_possible_cpumask in wq_numa_init() at boot time.
>>
>> When doing node online/offline, cpuid <-> nodeid mapping is established/destroyed,
>> which means, cpuid <-> nodeid mapping will change if node hotplug happens. But
>> workqueue does not update wq_numa_possible_cpumask.
> So why are you not fixing up wq_numa_possible_cpumask instead? That
> seems the far easier solution.

We tried to do that. You can see our patch at
http://www.gossamer-threads.com/lists/linux/kernel/2116748

But maintainer thought, we should establish persistent cpuid<->nodeid 
relationship,
there is no need to change the map.

Cc TJ,
Could we return to workqueue to fix this?

Thanks,
Zhu

> Do all the other archs that support NUMA and HOTPLUG have the mapping
> stable, or will you now go fix each and every one of them?
>
>
> .
>