linux-kernel - Re: [PATCH -V8 02/10] mm/numa: automatically generate node migration order

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Message-ID: <871r8uoh11.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date:   Tue, 22 Jun 2021 08:54:34 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Zi Yan <ziy@...dia.com>, Dave Hansen <dave.hansen@...ux.intel.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        Yang Shi <shy828301@...il.com>, Michal Hocko <mhocko@...e.com>,
        Wei Xu <weixugc@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Dan Williams <dan.j.williams@...el.com>,
        David Hildenbrand <david@...hat.com>,
        osalvador <osalvador@...e.de>
Subject: Re: [PATCH -V8 02/10] mm/numa: automatically generate node
 migration order

Dave Hansen <dave.hansen@...el.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