linux-kernel - [Patch V2 2/2] x86/mm/numa: remove the numa_nodemask_from

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Date:   Tue, 14 Mar 2017 11:08:01 +0800
From:   Wei Yang <richard.weiyang@...il.com>
To:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com, tj@...nel.org,
        bp@...en8.de
Cc:     linux-kernel@...r.kernel.org, Wei Yang <richard.weiyang@...il.com>
Subject: [Patch V2 2/2] x86/mm/numa: remove the numa_nodemask_from_meminfo()

numa_nodemask_from_meminfo() is called to set bit according to
numa_meminfo. While the only two places for this call is used to set proper
bit to a copy of numa_nodes_parsed from numa_meminfo. With current code
path, those numa node information in numa_meminfo is a subset of
numa_nodes_parsed. So it is not necessary to set the bits again.

The following is a code path analysis to prove the numa node information in
numa_meminfo is a subset of numa_nodes_parsed.

    x86_numa_init()
        numa_init()
            Case 1
            acpi_numa_init()
                acpi_parse_memory_affinity()
                    numa_add_memblk()
                    node_set(numa_nodes_parsed)
                acpi_parse_slit()
                    numa_nodemask_from_meminfo()

            Case 2
            amd_numa_init()
                numa_add_memblk()
                node_set(numa_nodes_parsed)

            Case 3
            dummy_numa_init()
                node_set(numa_nodes_parsed)
                numa_add_memblk()

            numa_register_memblks()
                numa_nodemask_from_meminfo()

>From the code path analysis, we can see each time a memblk is added, the
proper bit is set in numa_nodes_parsed, which means it is not necessary to
set it again in numa_nodemask_from_meminfo() for a copy of
numa_nodes_parsed.

This patch removes numa_nodemask_from_meminfo().

Signed-off-by: Wei Yang <richard.weiyang@...il.com>
---
 arch/x86/mm/numa.c | 21 +--------------------
 1 file changed, 1 insertion(+), 20 deletions(-)

diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index ac632e5397aa..5ecc5a745c51 100644
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -314,20 +314,6 @@ int __init numa_cleanup_meminfo(struct numa_meminfo *mi)
 	return 0;
 }
 
-/*
- * Set nodes, which have memory in @mi, in *@...emask.
- */
-static void __init numa_nodemask_from_meminfo(nodemask_t *nodemask,
-					      const struct numa_meminfo *mi)
-{
-	int i;
-
-	for (i = 0; i < ARRAY_SIZE(mi->blk); i++)
-		if (mi->blk[i].start != mi->blk[i].end &&
-		    mi->blk[i].nid != NUMA_NO_NODE)
-			node_set(mi->blk[i].nid, *nodemask);
-}
-
 /**
  * numa_reset_distance - Reset NUMA distance table
  *
@@ -347,16 +333,12 @@ void __init numa_reset_distance(void)
 
 static int __init numa_alloc_distance(void)
 {
-	nodemask_t nodes_parsed;
 	size_t size;
 	int i, j, cnt = 0;
 	u64 phys;
 
 	/* size the new table and allocate it */
-	nodes_parsed = numa_nodes_parsed;
-	numa_nodemask_from_meminfo(&nodes_parsed, &numa_meminfo);
-
-	for_each_node_mask(i, nodes_parsed)
+	for_each_node_mask(i, numa_nodes_parsed)
 		cnt = i;
 	cnt++;
 	size = cnt * cnt * sizeof(numa_distance[0]);
@@ -535,7 +517,6 @@ static int __init numa_register_memblks(struct numa_meminfo *mi)
 
 	/* Account for nodes with cpus and no memory */
 	node_possible_map = numa_nodes_parsed;
-	numa_nodemask_from_meminfo(&node_possible_map, mi);
 	if (WARN_ON(nodes_empty(node_possible_map)))
 		return -EINVAL;
 
-- 
2.11.0