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Message-ID: <20200402080144.GK22681@dhcp22.suse.cz>
Date: Thu, 2 Apr 2020 10:01:44 +0200
From: Michal Hocko <mhocko@...nel.org>
To: Mike Rapoport <rppt@...ux.ibm.com>
Cc: Baoquan He <bhe@...hat.com>,
Hoan Tran <Hoan@...amperecomputing.com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
Vlastimil Babka <vbabka@...e.cz>,
Oscar Salvador <osalvador@...e.de>,
Pavel Tatashin <pavel.tatashin@...rosoft.com>,
Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
"H. Peter Anvin" <hpa@...or.com>,
"David S. Miller" <davem@...emloft.net>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Vasily Gorbik <gor@...ux.ibm.com>,
Christian Borntraeger <borntraeger@...ibm.com>,
"open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>,
linux-arm-kernel@...ts.infradead.org, linux-s390@...r.kernel.org,
sparclinux@...r.kernel.org, x86@...nel.org,
linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
lho@...erecomputing.com, mmorana@...erecomputing.com
Subject: Re: [PATCH RFC] mm: remove CONFIG_HAVE_MEMBLOCK_NODE_MAP (was: Re:
[PATCH v3 0/5] mm: Enable CONFIG_NODES_SPAN_OTHER_NODES by default for NUMA)
On Wed 01-04-20 10:51:55, Mike Rapoport wrote:
> Hi,
>
> On Wed, Apr 01, 2020 at 01:42:27PM +0800, Baoquan He wrote:
[...]
> > From above information, we can remove HAVE_MEMBLOCK_NODE_MAP, and
> > replace it with CONFIG_NUMA. That sounds more sensible to store nid into
> > memblock when NUMA support is enabled.
>
> Replacing CONFIG_HAVE_MEMBLOCK_NODE_MAP with CONFIG_NUMA will work, but
> this will not help cleaning up the whole node/zone initialization mess and
> we'll be stuck with two implementations.
Yeah, this is far from optimal.
> The overhead of enabling HAVE_MEMBLOCK_NODE_MAP is only for init time as
> most architectures will anyway discard the entire memblock, so having it in
> a UMA arch won't be a problem. The only exception is arm that uses
> memblock for pfn_valid(), here we may also think about a solution to
> compensate the addition of nid to the memblock structures.
Well, we can make memblock_region->nid defined only for CONFIG_NUMA.
memblock_get_region_node would then unconditionally return 0 on UMA.
Essentially the same way we do NUMA for other MM code. I only see few
direct usage of region->nid.
--
Michal Hocko
SUSE Labs
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