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Date: Wed, 31 Jul 2019 13:40:16 +0200
From: Michal Hocko <mhocko@kernel.org>
To: Mike Rapoport <rppt@linux.ibm.com>
Subject: Re: [PATCH v2 0/5] mm: Enable CONFIG_NODES_SPAN_OTHER_NODES by
 default for NUMA
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Cc: Heiko Carstens <heiko.carstens@de.ibm.com>,
 "open list:MEMORY MANAGEMENT" <linux-mm@kvack.org>,
 Paul Mackerras <paulus@samba.org>, "H . Peter Anvin" <hpa@zytor.com>,
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 "x86@kernel.org" <x86@kernel.org>, "willy@infradead.org" <willy@infradead.org>,
 Christian Borntraeger <borntraeger@de.ibm.com>, Ingo Molnar <mingo@redhat.com>,
 Hoan Tran OS <hoan@os.amperecomputing.com>,
 Catalin Marinas <catalin.marinas@arm.com>,
 Open Source Submission <patches@amperecomputing.com>,
 Pavel Tatashin <pavel.tatashin@microsoft.com>,
 Vasily Gorbik <gor@linux.ibm.com>, Will Deacon <will.deacon@arm.com>,
 Borislav Petkov <bp@alien8.de>, Thomas Gleixner <tglx@linutronix.de>,
 Vlastimil Babka <vbabka@suse.cz>, Oscar Salvador <osalvador@suse.de>,
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 "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
 Andrew Morton <akpm@linux-foundation.org>,
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On Wed 31-07-19 14:14:22, Mike Rapoport wrote:
> On Wed, Jul 31, 2019 at 10:03:09AM +0200, Michal Hocko wrote:
> > On Wed 31-07-19 09:24:21, Mike Rapoport wrote:
> > > [ sorry for a late reply too, somehow I missed this thread before ]
> > > 
> > > On Tue, Jul 30, 2019 at 10:14:15AM +0200, Michal Hocko wrote:
> > > > [Sorry for a late reply]
> > > > 
> > > > On Mon 15-07-19 17:55:07, Hoan Tran OS wrote:
> > > > > Hi,
> > > > > 
> > > > > On 7/12/19 10:00 PM, Michal Hocko wrote:
> > > > [...]
> > > > > > Hmm, I thought this was selectable. But I am obviously wrong here.
> > > > > > Looking more closely, it seems that this is indeed only about
> > > > > > __early_pfn_to_nid and as such not something that should add a config
> > > > > > symbol. This should have been called out in the changelog though.
> > > > > 
> > > > > Yes, do you have any other comments about my patch?
> > > > 
> > > > Not really. Just make sure to explicitly state that
> > > > CONFIG_NODES_SPAN_OTHER_NODES is only about __early_pfn_to_nid and that
> > > > doesn't really deserve it's own config and can be pulled under NUMA.
> > > > 
> > > > > > Also while at it, does HAVE_MEMBLOCK_NODE_MAP fall into a similar
> > > > > > bucket? Do we have any NUMA architecture that doesn't enable it?
> > > > > > 
> > > 
> > > HAVE_MEMBLOCK_NODE_MAP makes huge difference in node/zone initialization
> > > sequence so it's not only about a singe function.
> > 
> > The question is whether we want to have this a config option or enable
> > it unconditionally for each NUMA system.
> 
> We can make it 'default NUMA', but we can't drop it completely because
> microblaze uses sparse_memory_present_with_active_regions() which is
> unavailable when HAVE_MEMBLOCK_NODE_MAP=n.

I suppose you mean that microblaze is using
sparse_memory_present_with_active_regions even without CONFIG_NUMA,
right? I have to confess I do not understand that code. What is the deal
with setting node id there?
-- 
Michal Hocko
SUSE Labs