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SubjectRe: [PATCH v6 00/15] memory-hotplug: hot-remove physical memory
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Hi Tang,
On Thu, 2013-01-31 at 15:10 +0800, Tang Chen wrote:
> On 01/31/2013 02:19 PM, Simon Jeons wrote:
> > Hi Tang,
> > On Thu, 2013-01-31 at 11:31 +0800, Tang Chen wrote:
> >> Hi Simon,
> >>
> >> Please see below. :)
> >>
> >> On 01/31/2013 09:22 AM, Simon Jeons wrote:
> >>>
> >>> Sorry, I still confuse. :(
> >>> update node_states[N_NORMAL_MEMORY] to node_states[N_MEMORY] or
> >>> node_states[N_NORMAL_MEMOR] present 0...ZONE_MOVABLE?
> >>>
> >>> node_states is what? node_states[N_NORMAL_MEMOR] or
> >>> node_states[N_MEMORY]?
> >>
> >> Are you asking what node_states[] is ?
> >>
> >> node_states[] is an array of nodemask,
> >>
> >> extern nodemask_t node_states[NR_NODE_STATES];
> >>
> >> For example, node_states[N_NORMAL_MEMOR] represents which nodes have
> >> normal memory.
> >> If N_MEMORY == N_HIGH_MEMORY == N_NORMAL_MEMORY, node_states[N_MEMORY] is
> >> node_states[N_NORMAL_MEMOR]. So it represents which nodes have 0 ...
> >> ZONE_MOVABLE.
> >>
> >
> > Sorry, how can nodes_state[N_NORMAL_MEMORY] represents a node have 0 ...
> > *ZONE_MOVABLE*, the comment of enum nodes_states said that
> > N_NORMAL_MEMORY just means the node has regular memory.
> >
>
> Hi Simon,
>
> Let's say it in this way.
>
> If we don't have CONFIG_HIGHMEM, N_HIGH_MEMORY == N_NORMAL_MEMORY. We
> don't have a separate
> macro to represent highmem because we don't have highmem.
> This is easy to understand, right ?
>
> Now, think it just like above:
> If we don't have CONFIG_MOVABLE_NODE, N_MEMORY == N_HIGH_MEMORY ==
> N_NORMAL_MEMORY.
> This means we don't allow a node to have only movable memory, not we
> don't have movable memory.
> A node could have normal memory and movable memory. So
> nodes_state[N_NORMAL_MEMORY] represents
> a node have 0 ... *ZONE_MOVABLE*.
>
> I think the point is: CONFIG_MOVABLE_NODE means we allow a node to have
> only movable memory.
> So without CONFIG_MOVABLE_NODE, it doesn't mean a node cannot have
> movable memory. It means
> the node cannot have only movable memory. It can have normal memory and
> movable memory.
>
> 1) With CONFIG_MOVABLE_NODE:
> N_NORMAL_MEMORY: nodes who have normal memory.
> normal memory only
> normal and highmem
> normal and highmem and movablemem
> normal and movablemem
> N_MEMORY: nodes who has memory (any memory)
> normal memory only
> normal and highmem
> normal and highmem and movablemem
> normal and movablemem ---------------- We can have
> movablemem.
> highmem only -------------------------
> highmem and movablemem ---------------
> movablemem only ---------------------- We can have
> movablemem only. ***
>
> 2) With out CONFIG_MOVABLE_NODE:
> N_MEMORY == N_NORMAL_MEMORY: (Here, I omit N_HIGH_MEMORY)
> normal memory only
> normal and highmem
> normal and highmem and movablemem
> normal and movablemem ---------------- We can have
> movablemem.
> No movablemem only ------------------- We cannot
> have movablemem only. ***
>
> The semantics is not that clear here. So we can only try to understand
> it from the code where
> we use N_MEMORY. :)
>
> That is my understanding of this.

Thanks for your clarify, very clear now. :)

>
> Thanks. :)
>
>
>
>
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