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

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:

quoted

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/ (local)

Regards,
Bharata.