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

[David Hildenbrand]

On 19.07.24 17:51, Jonathan Cameron wrote:
> On Fri, 19 Jul 2024 17:07:35 +0200
> David Hildenbrand <david@xxxxxxxxxx> 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