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SubjectRe: [PATCH v3 0/5] mm: Enable CONFIG_NODES_SPAN_OTHER_NODES by default for NUMA
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Hi All,

On 3/31/20 7:31 AM, Baoquan He wrote:
> On 03/31/20 at 04:21pm, Michal Hocko wrote:
>> On Tue 31-03-20 22:03:32, Baoquan He wrote:
>>> Hi Michal,
>>>
>>> On 03/31/20 at 10:55am, Michal Hocko wrote:
>>>> On Tue 31-03-20 11:14:23, Mike Rapoport wrote:
>>>>> Maybe I mis-read the code, but I don't see how this could happen. In the
>>>>> HAVE_MEMBLOCK_NODE_MAP=y case, free_area_init_node() calls
>>>>> calculate_node_totalpages() that ensures that node->node_zones are entirely
>>>>> within the node because this is checked in zone_spanned_pages_in_node().
>>>>
>>>> zone_spanned_pages_in_node does chech the zone boundaries are within the
>>>> node boundaries. But that doesn't really tell anything about other
>>>> potential zones interleaving with the physical memory range.
>>>> zone->spanned_pages simply gives the physical range for the zone
>>>> including holes. Interleaving nodes are essentially a hole
>>>> (__absent_pages_in_range is going to skip those).
>>>>
>>>> That means that when free_area_init_core simply goes over the whole
>>>> physical zone range including holes and that is why we need to check
>>>> both for physical and logical holes (aka other nodes).
>>>>
>>>> The life would be so much easier if the whole thing would simply iterate
>>>> over memblocks...
>>>
>>> The memblock iterating sounds a great idea. I tried with putting the
>>> memblock iterating in the upper layer, memmap_init(), which is used for
>>> boot mem only anyway. Do you think it's doable and OK? It yes, I can
>>> work out a formal patch to make this simpler as you said. The draft code
>>> is as below. Like this it uses the existing code and involves little change.
>>
>> Doing this would be a step in the right direction! I haven't checked the
>> code very closely though. The below sounds way too simple to be truth I
>> am afraid. First for_each_mem_pfn_range is available only for
>> CONFIG_HAVE_MEMBLOCK_NODE_MAP (which is one of the reasons why I keep
>> saying that I really hate that being conditional). Also I haven't really
>> checked the deferred initialization path - I have a very vague
>> recollection that it has been converted to the memblock api but I have
>> happilly dropped all that memory.
>
> Thanks for your quick response and pointing out the rest suspect aspects,
> I will investigate what you mentioned, see if they impact.

I would like to check if we still move on with my patch to remove
CONFIG_NODES_SPAN_OTHER_NODES and have another patch on top it?

Thanks
Hoan

>
>>
>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>> index 138a56c0f48f..558d421f294b 100644
>>> --- a/mm/page_alloc.c
>>> +++ b/mm/page_alloc.c
>>> @@ -6007,14 +6007,6 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
>>> * function. They do not exist on hotplugged memory.
>>> */
>>> if (context == MEMMAP_EARLY) {
>>> - if (!early_pfn_valid(pfn)) {
>>> - pfn = next_pfn(pfn);
>>> - continue;
>>> - }
>>> - if (!early_pfn_in_nid(pfn, nid)) {
>>> - pfn++;
>>> - continue;
>>> - }
>>> if (overlap_memmap_init(zone, &pfn))
>>> continue;
>>> if (defer_init(nid, pfn, end_pfn))
>>> @@ -6130,9 +6122,17 @@ static void __meminit zone_init_free_lists(struct zone *zone)
>>> }
>>>
>>> void __meminit __weak memmap_init(unsigned long size, int nid,
>>> - unsigned long zone, unsigned long start_pfn)
>>> + unsigned long zone, unsigned long range_start_pfn)
>>> {
>>> - memmap_init_zone(size, nid, zone, start_pfn, MEMMAP_EARLY, NULL);
>>> + unsigned long start_pfn, end_pfn;
>>> + unsigned long range_end_pfn = range_start_pfn + size;
>>> + int i;
>>> + for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
>>> + start_pfn = clamp(start_pfn, range_start_pfn, range_end_pfn);
>>> + end_pfn = clamp(end_pfn, range_start_pfn, range_end_pfn);
>>> + if (end_pfn > start_pfn)
>>> + memmap_init_zone(size, nid, zone, start_pfn, MEMMAP_EARLY, NULL);
>>> + }
>>> }
>>>
>>> static int zone_batchsize(struct zone *zone)
>>
>> --
>> Michal Hocko
>> SUSE Labs
>>
>

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