From: David Hildenbrand <david@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Andrew Morton <akpm@linux-foundation.org>,
Baoquan He <bhe@redhat.com>, Oscar Salvador <osalvador@suse.de>,
Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Subject: Re: [PATCH RFC 1/2] mm/memory_hotplug: no need to init new pgdat with node_start_pfn
Date: Tue, 21 Apr 2020 14:35:12 +0200 [thread overview]
Message-ID: <ac246ba8-9a61-0e0b-3aff-caf78743e81f@redhat.com> (raw)
In-Reply-To: <20200421123011.GE27314@dhcp22.suse.cz>
On 21.04.20 14:30, Michal Hocko wrote:
> Sorry for the late reply
>
> On Thu 16-04-20 12:47:06, David Hildenbrand wrote:
>> A hotadded node/pgdat will span no pages at all, until memory is moved to
>> the zone/node via move_pfn_range_to_zone() -> resize_pgdat_range - e.g.,
>> when onlining memory blocks. We don't have to initialize the
>> node_start_pfn to the memory we are adding.
>
> You are right that the node is empty at this phase but that is already
> reflected by zero present pages (hmm, I do not see spanned pages to be
> set 0 though). What I am missing here is why this is an improvement. The
> new node is already visible here and I do not see why we hide the
> information we already know.
"information we already know" - no, not before we online the memory.
Before onlining, it's just setting node_start_pfn to *some value* to be
overwritten in move_pfn_range_to_zone()->resize_pgdat_range().
(I have some more patches to clean up __try_online_node(), and this
change here makes it clear that there isn't any magic happening in
__try_online_node() related to the start pfn and memblocks - see patch #2)
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-04-21 12:35 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-16 10:47 [PATCH RFC 0/2] mm/memory_hotplug: handle memblocks only with CONFIG_ARCH_KEEP_MEMBLOCK David Hildenbrand
2020-04-16 10:47 ` [PATCH RFC 1/2] mm/memory_hotplug: no need to init new pgdat with node_start_pfn David Hildenbrand
2020-04-16 14:11 ` Pankaj Gupta
2020-04-21 12:30 ` Michal Hocko
2020-04-21 12:35 ` David Hildenbrand [this message]
2020-04-21 12:52 ` Michal Hocko
2020-04-21 13:06 ` David Hildenbrand
2020-04-22 8:21 ` Michal Hocko
2020-04-22 8:32 ` David Hildenbrand
2020-04-22 10:00 ` Michal Hocko
2020-04-16 10:47 ` [PATCH RFC 2/2] mm/memory_hotplug: handle memblocks only with CONFIG_ARCH_KEEP_MEMBLOCK David Hildenbrand
2020-04-16 17:09 ` Mike Rapoport
2020-04-21 12:39 ` Michal Hocko
2020-04-21 12:41 ` David Hildenbrand
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