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

Dave Hansen [off-list ref] writes:

On 6/19/21 1:18 AM, Huang, Ying wrote:

quoted

quoted

quoted

 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