Re: [PATCH] slub: Don't throw away partial remote slabs if there is no local memory

Wanpeng Li
2014-01-07T08:48:57Z

Hi Joonsoo,
On Tue, Jan 07, 2014 at 04:41:36PM +0900, Joonsoo Kim wrote:
>On Tue, Jan 07, 2014 at 01:21:00PM +1100, Anton Blanchard wrote:
>>
[...]
>Hello,
>
>I think that we need more efforts to solve unbalanced node problem.
>
>With this patch, even if node of current cpu slab is not favorable to
>unbalanced node, allocation would proceed and we would get the unintended memory.
>

We have a machine:

[ 0.000000] Node 0 Memory:
[ 0.000000] Node 4 Memory: 0x0-0x10000000 0x20000000-0x60000000 0x80000000-0xc0000000
[ 0.000000] Node 6 Memory: 0x10000000-0x20000000 0x60000000-0x80000000
[ 0.000000] Node 10 Memory: 0xc0000000-0x180000000

[ 0.041486] Node 0 CPUs: 0-19
[ 0.041490] Node 4 CPUs:
[ 0.041492] Node 6 CPUs:
[ 0.041495] Node 10 CPUs:

The pages of current cpu slab should be allocated from fallback zones/nodes
of the memoryless node in buddy system, how can not favorable happen?

>And there is one more problem. Even if we have some partial slabs on
>compatible node, we would allocate new slab, because get_partial() cannot handle
>this unbalance node case.
>
>To fix this correctly, how about following patch?
>

So I think we should fold both of your two patches to one.

Regards,
Wanpeng Li

>Thanks.
>
>------------->8--------------------
>diff --git a/mm/slub.c b/mm/slub.c
>index c3eb3d3..a1f6dfa 100644
>--- a/mm/slub.c
>+++ b/mm/slub.c
>@@ -1672,7 +1672,19 @@ static void *get_partial(struct kmem_cache *s, gfp_t flags, int node,
> {
> void *object;
> int searchnode = (node == NUMA_NO_NODE) ? numa_node_id() : node;
>+ struct zonelist *zonelist;
>+ struct zoneref *z;
>+ struct zone *zone;
>+ enum zone_type high_zoneidx = gfp_zone(flags);
>
>+ if (!node_present_pages(searchnode)) {
>+ zonelist = node_zonelist(searchnode, flags);
>+ for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
>+ searchnode = zone_to_nid(zone);
>+ if (node_present_pages(searchnode))
>+ break;
>+ }
>+ }
> object = get_partial_node(s, get_node(s, searchnode), c, flags);
> if (object || node != NUMA_NO_NODE)
> return object;
>
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