On Fri 30-07-21 11:05:02, Feng Tang wrote:

On Thu, Jul 29, 2021 at 06:21:19PM +0200, Michal Hocko wrote:

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On Thu 29-07-21 23:12:42, Feng Tang wrote:

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On Thu, Jul 29, 2021 at 03:38:44PM +0200, Michal Hocko wrote:

[...]

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Also the
semantic to give nodes some ordering based on their numbers sounds
rather weird to me.

I agree, and as I admitted in the first reply, this need to be fixed.

OK. I was not really clear that we are on the same page here.

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The semantic I am proposing is to allocate from prefered nodes in
distance order starting from the local node.

So the plan is:
* if the local node is set in 'prefer-many's nodemask, then chose
* otherwise chose the node with the shortest distance to local node
?

Yes and what I am trying to say is that you will achieve that simply by
doing the following in policy_node:
	if (policy->mode == MPOL_PREFERRED_MANY)
		return nd;

One thing is, it's possible that 'nd' is not set in the preferred
nodemask. 

Yes, and there shouldn't be any problem with that.  The given node is
only used to get the respective zonelist (order distance ordered list of
zones to try). get_page_from_freelist will then use the preferred node
mask to filter this zone list. Is that more clear now?
-- 
Michal Hocko
SUSE Labs