From: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: Zhang Yanfei <zhangyanfei.yes@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
"H. Peter Anvin" <hpa@zytor.com>, Tejun Heo <tj@kernel.org>,
Lai Jiangshan <laijs@cn.fujitsu.com>,
Wen Congyang <wency@cn.fujitsu.com>,
isimatu.yasuaki@jp.fujitsu.com, izumi.taku@jp.fujitsu.com,
Tang Chen <tangchen@cn.fujitsu.com>,
linux-doc@vger.kernel.org,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>,
imtangchen@gmail.com
Subject: Re: [PATCH -mm] mm, memory-hotpulg: Rename movablenode boot option to movable_node
Date: Tue, 01 Oct 2013 14:21:14 +0800 [thread overview]
Message-ID: <524A69DA.9050701@cn.fujitsu.com> (raw)
In-Reply-To: <20131001054646.GA17220@gmail.com>
Hello Ingo,
On 10/01/2013 01:46 PM, Ingo Molnar wrote:
>
> * Zhang Yanfei <zhangyanfei.yes@gmail.com> wrote:
>
>> @@ -153,11 +153,18 @@ config MOVABLE_NODE
>> help
>> Allow a node to have only movable memory. Pages used by the kernel,
>> such as direct mapping pages cannot be migrated. So the corresponding
>> + memory device cannot be hotplugged. This option allows the following
>> + two things:
>> + - When the system is booting, node full of hotpluggable memory can
>> + be arranged to have only movable memory so that the whole node can
>> + be hotplugged. (need movable_node boot option specified).
>
> So this is _exactly_ what I complained about earlier: why is the
> movable_node boot option needed to get that extra functionality? It's
> clearly not just a drop-in substitute to CONFIG_MOVABLE_NODE but extends
> its functionality, right?
Generally speaking, CONFIG_MOVABLE_NODE is used to allow a node to have
only movable memory. Firstly, we didn't support the functionality to support
boot-time configuration. That said, before this patchset, we only support
later hot-add node to have only movable memory but any node that is dectected
at boot-time cannot. So here is movable_node option, to protect the kernel
from using hotpluggable memory at boot-time and if a node is full of hotpluggable
memory, this node is arranged to have only movable memory and can be hot-removed
after the system is up.
>
> Boot options are _very_ poor user interface. If you don't want to enable
> it by default then turn this sub-functionality into
> CONFIG_MOVABLE_NODE_AUTO and keep it default-off - but don't pretend that
> this is only about CONFIG_MOVABLE_NODE alone - it isnt: as described above
> the 'movable_node' is needed for the full functionality to be available!
As explained above, we need the boot option to only disable boot-time
memory-hotplug configuration not the whole MOVABLE_NODE functionality.
Thanks
--
Thanks.
Zhang Yanfei
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prev parent reply other threads:[~2013-10-01 6:22 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-30 17:41 [PATCH -mm] mm, memory-hotpulg: Rename movablenode boot option to movable_node Zhang Yanfei
2013-10-01 5:46 ` Ingo Molnar
2013-10-01 6:21 ` Zhang Yanfei [this message]
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