x86-64: Combine SRAT regions when possible

... i.e. when the hole between two regions isn't occupied by memory on
another node. This reduces the memory->node table size, thus reducing
cache footprint of lookups, which got increased significantly some
time ago, and things go back to how they were before that change on
the systems I looked at.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
LKML-Reference: <4BCF3230020000780003B3CA@vpn.id2.novell.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/arch/x86/mm/srat_64.c b/arch/x86/mm/srat_64.c
index 28c68762648f..3ebe6519bd87 100644
--- a/arch/x86/mm/srat_64.c
+++ b/arch/x86/mm/srat_64.c
@@ -363,6 +363,54 @@ int __init acpi_scan_nodes(unsigned long start, unsigned long end)
         for (i = 0; i < MAX_NUMNODES; i++)
                 cutoff_node(i, start, end);
 
+        /*
+         * Join together blocks on the same node, holes between
+         * which don't overlap with memory on other nodes.
+         */
+        for (i = 0; i < num_node_memblks; ++i) {
+                int j, k;
+
+                for (j = i + 1; j < num_node_memblks; ++j) {
+                        unsigned long start, end;
+
+                        if (memblk_nodeid[i] != memblk_nodeid[j])
+                                continue;
+                        start = min(node_memblk_range[i].end,
+                                    node_memblk_range[j].end);
+                        end = max(node_memblk_range[i].start,
+                                  node_memblk_range[j].start);
+                        for (k = 0; k < num_node_memblks; ++k) {
+                                if (memblk_nodeid[i] == memblk_nodeid[k])
+                                        continue;
+                                if (start < node_memblk_range[k].end &&
+                                    end > node_memblk_range[k].start)
+                                        break;
+                        }
+                        if (k < num_node_memblks)
+                                continue;
+                        start = min(node_memblk_range[i].start,
+                                    node_memblk_range[j].start);
+                        end = max(node_memblk_range[i].end,
+                                  node_memblk_range[j].end);
+                        printk(KERN_INFO "SRAT: Node %d "
+                               "[%Lx,%Lx) + [%Lx,%Lx) -> [%lx,%lx)\n",
+                               memblk_nodeid[i],
+                               node_memblk_range[i].start,
+                               node_memblk_range[i].end,
+                               node_memblk_range[j].start,
+                               node_memblk_range[j].end,
+                               start, end);
+                        node_memblk_range[i].start = start;
+                        node_memblk_range[i].end = end;
+                        k = --num_node_memblks - j;
+                        memmove(memblk_nodeid + j, memblk_nodeid + j+1,
+                                k * sizeof(*memblk_nodeid));
+                        memmove(node_memblk_range + j, node_memblk_range + j+1,
+                                k * sizeof(*node_memblk_range));
+                        --j;
+                }
+        }
+
         memnode_shift = compute_hash_shift(node_memblk_range, num_node_memblks,
                                            memblk_nodeid);
         if (memnode_shift < 0) {