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.
Why check !z1->wait_table in function move_pfn_range_left and function
__add_zone? I think zone->wait_table is initialized in
free_area_init_core, which will be called during system initialization
and hotadd_new_pgdat path.
I think,
free_area_init_core(), in the for loop,
|--> size = zone_spanned_pages_in_node();
|--> if (!size)
continue; ---------------- If zone is empty, we jump
out the for loop.
|--> init_currently_empty_zone()
So, if the zone is empty, wait_table is not initialized.
In move_pfn_range_left(z1, z2), we move pages from z2 to z1. But z1
could be empty.
So we need to check it and initialize z1->wait_table because we are
moving pages into it.
There is a zone populated check in function online_pages. But zone is
populated in free_area_init_core which will be called during system
initialization and hotadd_new_pgdat path. Why still need this check?
Because we could also rebuild zone list when we offline pages.
__offline_pages()
|--> zone->present_pages -= offlined_pages;
|--> if (!populated_zone(zone)) {
build_all_zonelists(NULL, NULL);
}
If the zone is empty, and other zones on the same node is not empty, the
node
won't be offlined, and next time we online pages of this zone, the pgdat
won't
be initialized again, and we need to check populated_zone(zone) when
onlining
pages.
Thanks. :)
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