2013/01/17 7:52, H. Peter Anvin wrote:
On 01/16/2013 01:29 PM, Andrew Morton wrote:
Yes. If SRAT support is available, all memory which enabled hotpluggable
bit are managed by ZONEMOVABLE. But performance degradation may
occur by NUMA because we can only allocate anonymous page and page-cache
from these memory.
In this case, if user cannot change SRAT information, user needs a way to
select/set removable memory manually.
If I understand this correctly you mean that once SRAT parsing is
implemented, the user can use movablecore_map to override that SRAT
parsing, yes? That movablecore_map will take precedence over SRAT?
Yes, but we still need a higher-level user interface which specifies
which nodes, not which memory ranges, should be movable.
I thought about the method of specifying the node. But I think
this method is inconvenience. Node number is decided by OS.
So the number is changed easily.
for example:
o exmaple 1
System has 3 nodes:
node0, node1, node2
When user remove node1, the system has:
node0, node2
But after rebooting the system, the system has:
node0, node1
So node2 becomes node1.
o example 2:
System has 2 nodes:
0x40000000 - 0x7fffffff : node0
0xc0000000 - 0xffffffff : node1
When user add a node wchih memory range is [0x80000000 - 0xbfffffff],
system has:
0x40000000 - 0x7fffffff : node0
0xc0000000 - 0xffffffff : node1
0x80000000 - 0xbfffffff : node2
But after rebooting the system, the system's node may become:
0x40000000 - 0x7fffffff : node0
0x80000000 - 0xbfffffff : node1
0xc0000000 - 0xffffffff : node2
So node nunber is changed.
Specifying node number may be easy method than specifying memory
range. But if user uses node number for specifying removable memory,
user always need to care whether node number is changed or not at
every hotplug operation.
Thanks,
Yasuaki Ishimatsu
That is the
policy granularity that is actually appropriate for the administrator
(trading off performance vs reliability.)
-hpa
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