Re: [PATCH 1/1] mem-hotplug: Handle node hole when initializing numa_meminfo.

Tang Chen
2015-07-03T01:26:06Z

On 07/02/2015 11:02 PM, Yasuaki Ishimatsu wrote:
> Hi Tang,
>
>> On my box, if I run lscpu, the output looks like this:
>>
>> 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
>>
>> Node 2 and 3 are not exist, but they are online.
> According your description of patch, node 4 and 5 are mistakenly

Not node 4 and 5, it is node 2 and 3 which are mistakenly set online.
> set to online. Why does lscpu show the above result?

Well, actually not only lscpu gives the strange result, under
/sys/device/system/node,
interfaces for node 2 and 3 are also created.

I haven't read lscpu code, so I'm not sure how lscpu handles nodes. But
obviously,
node 2 and 3 are set online, which is incorrect.

For now, I only found that in numa_cleanup_meminfo(), memory above
max_pfn is removed,
but holes between nodes are not removed.

I think libraries are not able to handle this problem since nodes are
set online in kernel.
Seeing from user space, there is no hole.

Thanks.

>
> Thanks,
> Yasuaki Ishimatsu
>
> On Wed, 1 Jul 2015 15:55:30 +0800
> Tang Chen <tangchen@cn.fujitsu.com> wrote:
>
>> On 07/01/2015 02:25 PM, Xishi Qiu wrote:
>>> On 2015/7/1 11:16, Tang Chen wrote:
>>>
>>>> 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.
>>>>
>>>> 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.
>>>>
>>> Hi Tang Chen,
>>>
>>> What's the impact of this problem?
>>>
>>> Command "numactl --hard" will show an empty node(no cpu and no memory,
>>> but pgdat is created), right?
>> On my box, if I run lscpu, the output looks like this:
>>
>> 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
>>
>> Node 2 and 3 are not exist, but they are online.
>>
>> Thanks.
>>
>>> Thanks,
>>> Xishi Qiu
>>>
>>>> Signed-off-by: Tang Chen <tangchen@cn.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..0c55cc5 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) == -1)
>>>> numa_remove_memblk_from(i--, mi);
>>>> }
>>>>
>>>> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
>>>> index 0215ffd..3bf6cc1 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);
>>>> +long 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 1b444c7..55b5f9f 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 long __init_memblock memblock_overlaps_region(struct memblock_type *type,
>>>> +long __init_memblock memblock_overlaps_region(struct memblock_type *type,
>>>> phys_addr_t base, phys_addr_t size)
>>>> {
>>>> unsigned long i;
>>>
>>> .
>>>
> .
>