Re: [Patch v2 2/2] mm/page_alloc: not necessary to multiply MAX_NODE_LOAD

[Wei Yang <richard.weiyang@gmail.com>]

On Mon, Apr 11, 2022 at 12:52:33PM +0200, Vlastimil Babka wrote:
>On 4/9/22 01:07, Wei Yang wrote:
>> On Fri, Apr 08, 2022 at 10:09:48AM +0200, David Hildenbrand wrote:
>>>On 08.04.22 04:59, Wei Yang wrote:
>>>> Since we just increase a constance of 1 to node penalty, it is not
>>>> necessary to multiply MAX_NODE_LOAD for preference.
>>>> 
>>>> This patch also remove the definition.
>>>> 
>>>> [vbabka@suse.cz: suggests]
>>>> 
>>>> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
>>>> CC: Vlastimil Babka <vbabka@suse.cz>
>>>> CC: David Hildenbrand <david@redhat.com>
>>>> CC: Oscar Salvador <osalvador@suse.de>
>>>> ---
>>>>  mm/page_alloc.c | 3 +--
>>>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>>> 
>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>>> index 86b6573fbeb5..ca6a127bbc26 100644
>>>> --- a/mm/page_alloc.c
>>>> +++ b/mm/page_alloc.c
>>>> @@ -6170,7 +6170,6 @@ int numa_zonelist_order_handler(struct ctl_table *table, int write,
>>>>  }
>>>>  
>>>>  
>>>> -#define MAX_NODE_LOAD (nr_online_nodes)
>>>>  static int node_load[MAX_NUMNODES];
>>>>  
>>>>  /**
>>>> @@ -6217,7 +6216,7 @@ int find_next_best_node(int node, nodemask_t *used_node_mask)
>>>>  			val += PENALTY_FOR_NODE_WITH_CPUS;
>>>>  
>>>>  		/* Slight preference for less loaded node */
>>>> -		val *= (MAX_NODE_LOAD*MAX_NUMNODES);
>>>> +		val *= MAX_NUMNODES;
>>>>  		val += node_load[n];
>>>>  
>>>>  		if (val < min_val) {
>>>
>>>I feel like this should be squashed into the previous patch. It has the
>>>same effect of making this code independent of nr_online_nodes. And I
>>>had to scratch my head a couple of times in patch #1 why the change in
>>>patch #1 is fine with thus remaining in place.
>>>
>>>
>>>Having that said, I consider this code highly unnecessary
>>>over-complicated at first sight. Removing some of the magic most
>>>certainly is very welcome.
>>>
>>>This semantics of the global variable node_load[] remains mostly
>>>mysterious for me.
>
>Looks like after this patch(es), it would be "how many times was this node
>picked as the first fallback out of nodes with the same distance"?
>
>>>
>> 
>> So the suggestion is a v3 with #1 and #2 squashed?
>
>Yes, and I agree with the suggestion.

No problem.

>
>>>-- 
>>>Thanks,
>>>
>>>David / dhildenb
>> 

-- 
Wei Yang
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