Slub: Increased mem consumption on cpu,mem-less node powerpc guest

[Vlastimil Babka]

On 3/17/20 12:53 PM, Bharata B Rao wrote:
> On Tue, Mar 17, 2020 at 02:56:28PM +0530, Bharata B Rao wrote:
>> Case 1: 2 node NUMA, node0 empty
>> ================================
>> # numactl -H
>> available: 2 nodes (0-1)
>> node 0 cpus:
>> node 0 size: 0 MB
>> node 0 free: 0 MB
>> node 1 cpus: 0 1 2 3 4 5 6 7
>> node 1 size: 16294 MB
>> node 1 free: 15453 MB
>> node distances:
>> node   0   1 
>>   0:  10  40 
>>   1:  40  10 
>> 
>> diff --git a/mm/slub.c b/mm/slub.c
>> index 17dc00e33115..888e4d245444 100644
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -1971,10 +1971,8 @@ static void *get_partial(struct kmem_cache *s, gfp_t flags, int node,
>>  	void *object;
>>  	int searchnode = node;
>>  
>> -	if (node == NUMA_NO_NODE)
>> +	if (node == NUMA_NO_NODE || !node_present_pages(node))
>>  		searchnode = numa_mem_id();
>> -	else if (!node_present_pages(node))
>> -		searchnode = node_to_mem_node(node);
> 
> For the above topology, I see this:
> 
> node_to_mem_node(1) = 1
> node_to_mem_node(0) = 0
> node_to_mem_node(NUMA_NO_NODE) = 0
> 
> Looks like the last two cases (returning memory-less node 0) is the
> problem here?

I wonder why do you get a memory leak while Sachin in the same situation [1]
gets a crash? I don't understand anything anymore.

[1]
https://lore.kernel.org/linux-next/3381CD91-AB3D-4773-BA04-E7A072A63968@linux.vnet.ibm.com/

> Regards,
> Bharata.
> 
>