From: Michal Hocko <mhocko@kernel.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>,
akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/memory_hotplug: just build zonelist for new added node
Date: Wed, 28 Jun 2017 11:45:16 +0200 [thread overview]
Message-ID: <20170628094516.GE5225@dhcp22.suse.cz> (raw)
In-Reply-To: <f92958f9-e831-8dc7-f8e6-2f4a46171e71@suse.cz>
On Wed 28-06-17 11:35:00, Vlastimil Babka wrote:
> On 06/28/2017 11:23 AM, Michal Hocko wrote:
> > On Mon 26-06-17 11:58:22, Wei Yang wrote:
> >> In commit (9adb62a5df9c0fbef7) "mm/hotplug: correctly setup fallback
> >> zonelists when creating new pgdat" tries to build the correct zonelist for
> >> a new added node, while it is not necessary to rebuild it for already exist
> >> nodes.
> >>
> >> In build_zonelists(), it will iterate on nodes with memory. For a new added
> >> node, it will have memory until node_states_set_node() is called in
> >> online_pages().
> >>
> >> This patch will avoid to rebuild the zonelists for already exist nodes.
> >
> > It is not very clear from the changelog why that actually matters. The
> > only effect I can see is that other zonelists on other online nodes will
> > not learn about the currently memory less node. This is a good think
> > because we do not pointlessly try to allocate from that node.
>
> build_zonelists_node() seems to use managed_zone(zone) checks, so it
> should not include empty zones anyway. So effectively seems to me we
> just avoid some pointless work under stop_machine().
Ohh, you are right. I was looking for populated_zone and didn't find any
so I thought we just do not care. So, indeed the patch has no functional
effect it just reduces the stop_machine overhead tiny bit.
--
Michal Hocko
SUSE Labs
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prev parent reply other threads:[~2017-06-28 9:45 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-26 3:58 Wei Yang
2017-06-28 7:06 ` Vlastimil Babka
2017-06-28 7:28 ` Wei Yang
2017-06-28 9:23 ` Michal Hocko
2017-06-28 9:35 ` Vlastimil Babka
2017-06-28 9:45 ` Michal Hocko [this message]
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