Re: [Part1 PATCH v5 13/22] x86, mm, numa: Use numa_meminfo to checknode_map_pfn alignment

From: Tejun Heo
Date: Mon Jun 17 2013 - 21:40:56 EST

On Thu, Jun 13, 2013 at 09:03:00PM +0800, Tang Chen wrote:
> From: Yinghai Lu <yinghai@xxxxxxxxxx>
> We could use numa_meminfo directly instead of memblock nid in
> node_map_pfn_alignment().
> So we could do setting memblock nid later and only do it once
> for successful path.
> -v2: according to tj, separate moving to another patch.

How about something like,

Subject: x86, mm, NUMA: Use numa_meminfo instead of memblock in node_map_pfn_alignment()

When sparsemem is used and page->flags doesn't have enough space to
carry both the sparsemem section and node ID, NODE_NOT_IN_PAGE_FLAGS
is set and the node is determined from section. This requires that
the NUMA nodes aren't more granular than sparsemem sections.
node_map_pfn_alignment() is used to determine the maximum NUMA
inter-node alignment which can distinguish all nodes to verify the
above condition.

The function currently assumes the NUMA node maps are populated and
sorted and uses for_each_mem_pfn_range() to iterate memory regions.
We want this to happen way earlier to support memory hotplug (maybe
elaborate a bit more here).

This patch updates node_map_pfn_alignment() so that it iterates over
numa_meminfo instead and moves its invocation before memory regions
are registered to memblock and node maps in numa_register_memblks().
This will help memory hotplug (how...) and as a bonus we register
memory regions only if the alignment check succeeds rather than
registering and then failing.

Also, the comment on top of node_map_pfn_alignment() needs to be
updated, right?


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