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From:   "Huang, Ying" <ying.huang@intel.com>
To:     Dave Hansen <dave.hansen@intel.com>
Cc:     Zi Yan <ziy@nvidia.com>, Dave Hansen <dave.hansen@linux.intel.com>,
        <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
        Yang Shi <shy828301@gmail.com>, Michal Hocko <mhocko@suse.com>,
        Wei Xu <weixugc@google.com>,
        David Rientjes <rientjes@google.com>,
        Dan Williams <dan.j.williams@intel.com>,
        David Hildenbrand <david@redhat.com>,
        osalvador <osalvador@suse.de>
Subject: Re: [PATCH -V8 02/10] mm/numa: automatically generate node
 migration order
References: <20210618061537.434999-1-ying.huang@intel.com>
        <20210618061537.434999-3-ying.huang@intel.com>
        <79397FE3-4B08-4DE5-8468-C5CAE36A3E39@nvidia.com>
        <87v96anu6o.fsf@yhuang6-desk2.ccr.corp.intel.com>
        <36307d7a-6e39-b1dd-64e8-95ec59f16867@intel.com>
Date:   Tue, 22 Jun 2021 08:54:34 +0800
In-Reply-To: <36307d7a-6e39-b1dd-64e8-95ec59f16867@intel.com> (Dave Hansen's
        message of "Mon, 21 Jun 2021 12:53:04 -0700")
Message-ID: <871r8uoh11.fsf@yhuang6-desk2.ccr.corp.intel.com>
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Dave Hansen <dave.hansen@intel.com> writes:

> On 6/19/21 1:18 AM, Huang, Ying wrote:
>>>>  int next_demotion_node(int node)
>>>>  {
>>>> -	return node_demotion[node];
>>>> +	/*
>>>> +	 * node_demotion[] is updated without excluding
>>>> +	 * this function from running.  READ_ONCE() avoids
>>>> +	 * reading multiple, inconsistent 'node' values
>>>> +	 * during an update.
>>>> +	 */
>>>> +	return READ_ONCE(node_demotion[node]);
>>>>  }
>>> Is it necessary to have two separate patches to add node_demotion and
>>> next_demotion_node() then modify it immediately? Maybe merge Patch 1 into 2?
>>>
>>> Hmm, I just checked Patch 3 and it changes node_demotion again and uses RCU.
>>> I guess it might be much simpler to just introduce node_demotion with RCU
>>> in this patch and Patch 3 only takes care of hotplug events.
>> Hi, Dave,
>> 
>> What do you think about this?
>> 
>
> Squashing them seems like a good idea to me.

Sure.  Will do that.  How about move RCU from 3/10 to the squashed one?

Best Regards,
Huang, Ying