Re: [PATCH 05/17] arch, mm: pull out allocation of NODE_DATA to generic code

On 19.07.24 17:51, Jonathan Cameron wrote:
> On Fri, 19 Jul 2024 17:07:35 +0200
> David Hildenbrand <[email protected]> wrote:
> 
>>>>> -	 * Allocate node data.  Try node-local memory and then any node.
>>>>> -	 * Never allocate in DMA zone.
>>>>> -	 */
>>>>> -	nd_pa = memblock_phys_alloc_try_nid(nd_size, SMP_CACHE_BYTES, nid);
>>>>> -	if (!nd_pa) {
>>>>> -		pr_err("Cannot find %zu bytes in any node (initial node: %d)\n",
>>>>> -		       nd_size, nid);
>>>>> -		return;
>>>>> -	}
>>>>> -	nd = __va(nd_pa);
>>>>> -
>>>>> -	/* report and initialize */
>>>>> -	printk(KERN_INFO "NODE_DATA(%d) allocated [mem %#010Lx-%#010Lx]\n", nid,
>>>>> -	       nd_pa, nd_pa + nd_size - 1);
>>>>> -	tnid = early_pfn_to_nid(nd_pa >> PAGE_SHIFT);
>>>>> -	if (tnid != nid)
>>>>> -		printk(KERN_INFO "    NODE_DATA(%d) on node %d\n", nid, tnid);
>>>>> -
>>>>> -	node_data[nid] = nd;
>>>>> -	memset(NODE_DATA(nid), 0, sizeof(pg_data_t));
>>>>> -
>>>>> -	node_set_online(nid);
>>>>> -}
>>>>> -
>>>>>     /**
>>>>>      * numa_cleanup_meminfo - Cleanup a numa_meminfo
>>>>>      * @mi: numa_meminfo to clean up
>>>>> @@ -571,6 +538,7 @@ static int __init numa_register_memblks(struct numa_meminfo *mi)
>>>>>     			continue;
>>>>>     		alloc_node_data(nid);
>>>>> +		node_set_online(nid);
>>>>>     	}
>>>>
>>>> I can spot that we only remove a single node_set_online() call from x86.
>>>>
>>>> What about all the other architectures? Will there be any change in behavior
>>>> for them? Or do we simply set the nodes online later once more?
>>>
>>> On x86 node_set_online() was a part of alloc_node_data() and I moved it
>>> outside so it's called right after alloc_node_data(). On other
>>> architectures the allocation didn't include that call, so there should be
>>> no difference there.
>>
>> But won't their arch code try setting the nodes online at a later stage?
>>
>> And I think, some architectures only set nodes online conditionally
>> (see most other node_set_online() calls).
>>
>> Sorry if I'm confused here, but with now unconditional node_set_online(), won't
>> we change the behavior of other architectures?
> This is moving x86 code to x86 code, not a generic location
> so how would that affect anyone else? Their onlining should be same as
> before.

Yes, see my reply to Mike.

> 
> The node onlining difference are a pain (I recall that fun from adding
> generic initiators) as different ordering on x86 and arm64 at least.

That's part of the reason I was confused, because I remember some nasty 
inconsistency.

-- 
Cheers,

David / dhildenb