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    SubjectRe: [PATCH v5 6/6] mem-hotplug: Introduce movablenode boot option
    On Wed, Sep 25, 2013 at 02:35:14AM +0800, Zhang Yanfei wrote:
    > From: Tang Chen <tangchen@cn.fujitsu.com>
    >
    > The hot-Pluggable field in SRAT specifies which memory is hotpluggable.
    > As we mentioned before, if hotpluggable memory is used by the kernel,
    > it cannot be hot-removed. So memory hotplug users may want to set all
    > hotpluggable memory in ZONE_MOVABLE so that the kernel won't use it.
    >
    > Memory hotplug users may also set a node as movable node, which has
    > ZONE_MOVABLE only, so that the whole node can be hot-removed.
    >
    > But the kernel cannot use memory in ZONE_MOVABLE. By doing this, the
    > kernel cannot use memory in movable nodes. This will cause NUMA
    > performance down. And other users may be unhappy.
    >
    > So we need a way to allow users to enable and disable this functionality.
    > In this patch, we introduce movablenode boot option to allow users to
    > choose to not to consume hotpluggable memory at early boot time and
    > later we can set it as ZONE_MOVABLE.
    >
    > To achieve this, the movablenode boot option will control the memblock
    > allocation direction. That said, after memblock is ready, before SRAT is
    > parsed, we should allocate memory near the kernel image as we explained
    > in the previous patches. So if movablenode boot option is set, the kernel
    > does the following:
    >
    > 1. After memblock is ready, make memblock allocate memory bottom up.
    > 2. After SRAT is parsed, make memblock behave as default, allocate memory
    > top down.
    >
    > Users can specify "movablenode" in kernel commandline to enable this
    > functionality. For those who don't use memory hotplug or who don't want
    > to lose their NUMA performance, just don't specify anything. The kernel
    > will work as before.
    >
    > Suggested-by: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    > Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
    > Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>

    I hope the param description and comment were better. Not necessarily
    longer, but clearer, so it'd be great if you can polish them a bit
    more. Other than that,

    Acked-by: Tejun Heo <tj@kernel.org>

    Thanks.

    --
    tejun


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