mm/page_alloc: add penalty to local_node

mm/page_alloc: add penalty to local_node

Commit 54d032ced983 ("mm/page_alloc: use accumulated load when building
node fallback list") fixed a bug on zonelist order.  This made me think
about what would happen if we have a node system with the following
distance matrix.

   Node 0  1  2  3  4  5  6  7
   ----------------------------
   0    10 12 12 12 32 32 32 32
   1    12 10 12 12 32 32 32 32
   2    12 12 10 12 32 32 32 32
   3    12 12 12 10 32 32 32 32
   4    32 32 32 32 10 12 12 12
   5    32 32 32 32 12 10 12 12
   6    32 32 32 32 12 12 10 12
   7    32 32 32 32 12 12 12 10

Unfortunately for this case, the node fallback list gets built like this:

   Node Fallback list
   ---------------------
    0:   0  1  2  3  4  5  6  7
    1:   1  0  2  3  5  6  7  4
    2:   2  3  0  1  6  7  4  5
    3:   3  2  0  1  7  4  5  6
    4:   4  5  6  7  0  1  2  3
    5:   5  4  6  7  1  2  3  0
    6:   6  7  4  5  2  3  0  1
    7:   7  6  4  5  3  0  1  2

We found the order in diagonal block is not expected.  The reason is we
don't penaltize local node.

After penalizing local node, the node fallback list gets built like this:

   Node Fallback list
   ---------------------
   0:   0  1  2  3  4  5  6  7
   1:   1  2  3  0  5  6  7  4
   2:   2  3  0  1  6  7  4  5
   3:   3  0  1  2  7  4  5  6
   4:   4  5  6  7  0  1  2  3
   5:   5  6  7  4  1  2  3  0
   6:   6  7  4  5  2  3  0  1
   7:   7  4  5  6  3  0  1  2

Now the fallback list is in round-robin order.

I am not very familiar with the node distance pattern, while I tried the
following distance matrix.  Both of them works with this change.

   Node 0  1  2  3
   ----------------
   0    10 10 10 10
   1    10 10 10 10
   2    10 10 10 10
   3    10 10 10 10

   Node 0  1  2  3  4  5  6  7
   ----------------------------
   0    10 10 10 10 32 32 32 32
   1    10 10 10 10 32 32 32 32
   2    10 10 10 10 32 32 32 32
   3    10 10 10 10 32 32 32 32
   4    32 32 32 32 10 10 10 10
   5    32 32 32 32 10 10 10 10
   6    32 32 32 32 10 10 10 10
   7    32 32 32 32 10 10 10 10

Link: https://lkml.kernel.org/r/20220123013537.20491-2-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Krupa Ramakrishnan <krupa.ramakrishnan@amd.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>