linux-kernel - [PATCH 2/2] mem-hotplug: Handle node hole when initializing numa

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Date:	Fri, 17 Jul 2015 09:23:31 +0800
From:	Tang Chen <tangchen@...fujitsu.com>
To:	<tglx@...utronix.de>, <mingo@...hat.com>, <hpa@...or.com>,
	<akpm@...ux-foundation.org>, <tj@...nel.org>, <dyoung@...hat.com>,
	<isimatu.yasuaki@...fujitsu.com>, <yasu.isimatu@...il.com>,
	<lcapitulino@...hat.com>, <qiuxishi@...wei.com>,
	<will.deacon@....com>, <tony.luck@...el.com>,
	<vladimir.murzin@....com>, <fabf@...net.be>,
	<kuleshovmail@...il.com>, <bhe@...hat.com>
CC:	<x86@...nel.org>, <tangchen@...fujitsu.com>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
Subject: [PATCH 2/2] mem-hotplug: Handle node hole when initializing numa_meminfo.

When parsing SRAT, all memory ranges are added into numa_meminfo.
In numa_init(), before entering numa_cleanup_meminfo(), all possible
memory ranges are in numa_meminfo. And numa_cleanup_meminfo() removes
all ranges over max_pfn or empty.

But, this only works if the nodes are continuous. Let's have a look
at the following example:

We have an SRAT like this:
SRAT: Node 0 PXM 0 [mem 0x00000000-0x5fffffff]
SRAT: Node 0 PXM 0 [mem 0x100000000-0x1ffffffffff]
SRAT: Node 1 PXM 1 [mem 0x20000000000-0x3ffffffffff]
SRAT: Node 4 PXM 2 [mem 0x40000000000-0x5ffffffffff] hotplug
SRAT: Node 5 PXM 3 [mem 0x60000000000-0x7ffffffffff] hotplug
SRAT: Node 2 PXM 4 [mem 0x80000000000-0x9ffffffffff] hotplug
SRAT: Node 3 PXM 5 [mem 0xa0000000000-0xbffffffffff] hotplug
SRAT: Node 6 PXM 6 [mem 0xc0000000000-0xdffffffffff] hotplug
SRAT: Node 7 PXM 7 [mem 0xe0000000000-0xfffffffffff] hotplug

On boot, only node 0,1,2,3 exist.

And the numa_meminfo will look like this:
numa_meminfo.nr_blks = 9
1. on node 0: [0, 60000000]
2. on node 0: [100000000, 20000000000]
3. on node 1: [20000000000, 40000000000]
4. on node 4: [40000000000, 60000000000]
5. on node 5: [60000000000, 80000000000]
6. on node 2: [80000000000, a0000000000]
7. on node 3: [a0000000000, a0800000000]
8. on node 6: [c0000000000, a0800000000]
9. on node 7: [e0000000000, a0800000000]

And numa_cleanup_meminfo() will merge 1 and 2, and remove 8,9 because
the end address is over max_pfn, which is a0800000000. But 4 and 5
are not removed because their end addresses are less then max_pfn.
But in fact, node 4 and 5 don't exist.

In a word, numa_cleanup_meminfo() is not able to handle holes between nodes.

Since memory ranges in node 4 and 5 are in numa_meminfo, in numa_register_memblks(),
node 4 and 5 will be mistakenly set to online.

If you run lscpu, it will show:
NUMA node0 CPU(s):     0-14,128-142
NUMA node1 CPU(s):     15-29,143-157
NUMA node2 CPU(s):
NUMA node3 CPU(s):
NUMA node4 CPU(s):     62-76,190-204
NUMA node5 CPU(s):     78-92,206-220

In this patch, we use memblock_overlaps_region() to check if ranges in
numa_meminfo overlap with ranges in memory_block. Since memory_block contains
all available memory at boot time, if they overlap, it means the ranges
exist. If not, then remove them from numa_meminfo.

After this patch, lscpu will show:
NUMA node0 CPU(s):     0-14,128-142
NUMA node1 CPU(s):     15-29,143-157
NUMA node4 CPU(s):     62-76,190-204
NUMA node5 CPU(s):     78-92,206-220

Signed-off-by: Tang Chen <tangchen@...fujitsu.com>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
---
 arch/x86/mm/numa.c       | 6 ++++--
 include/linux/memblock.h | 2 ++
 mm/memblock.c            | 2 +-
 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index 4053bb5..c3b3f65 100644
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -246,8 +246,10 @@ int __init numa_cleanup_meminfo(struct numa_meminfo *mi)
 		bi->start = max(bi->start, low);
 		bi->end = min(bi->end, high);
 
-		/* and there's no empty block */
-		if (bi->start >= bi->end)
+		/* and there's no empty or non-exist block */
+		if (bi->start >= bi->end ||
+		    !memblock_overlaps_region(&memblock.memory,
+			bi->start, bi->end - bi->start))
 			numa_remove_memblk_from(i--, mi);
 	}
 
diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index d312ae3..c518eb5 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -77,6 +77,8 @@ int memblock_remove(phys_addr_t base, phys_addr_t size);
 int memblock_free(phys_addr_t base, phys_addr_t size);
 int memblock_reserve(phys_addr_t base, phys_addr_t size);
 void memblock_trim_memory(phys_addr_t align);
+bool memblock_overlaps_region(struct memblock_type *type,
+			      phys_addr_t base, phys_addr_t size);
 int memblock_mark_hotplug(phys_addr_t base, phys_addr_t size);
 int memblock_clear_hotplug(phys_addr_t base, phys_addr_t size);
 int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
diff --git a/mm/memblock.c b/mm/memblock.c
index f1e7100..7f665d8 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -91,7 +91,7 @@ static unsigned long __init_memblock memblock_addrs_overlap(phys_addr_t base1, p
 	return ((base1 < (base2 + size2)) && (base2 < (base1 + size1)));
 }
 
-static bool __init_memblock memblock_overlaps_region(struct memblock_type *type,
+bool __init_memblock memblock_overlaps_region(struct memblock_type *type,
 					phys_addr_t base, phys_addr_t size)
 {
 	unsigned long i;
-- 
1.8.3.1

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