Hi Ying,
On 2023/10/23 09:18, Huang, Ying wrote:
Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> writes:
Hi Ying,
On 2023/10/20 15:05, Huang, Ying wrote:
Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> writes:
In offline_pages(), if a node becomes memoryless, we
will clear its N_MEMORY state by calling node_states_clear_node().
But we do this after rebuilding the zonelists by calling
build_all_zonelists(), which will cause this memoryless node to
still be in the fallback list of other nodes.
For fallback list, do you mean pgdat->node_zonelists[]? If so, in
build_all_zonelists
__build_all_zonelists
build_zonelists
build_zonelists_in_node_order
build_zonerefs_node
populated_zone() will be checked before adding zone into zonelist.
So, IIUC, we will not try to allocate from the memory less node.
Normally yes, but if it is the weird topology mentioned in [1], it's
possible to allocate memory from it, it is a memoryless node, but it
also has memory.
In addition to the above case, I think it's reasonable to remove
memory less node from node_order[] in advance. In this way it will
not to be traversed in build_zonelists_in_node_order().
[1]. https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@xxxxxxxxxxxxx/
Got it! Thank you for information. I think that it may be good to
include this in the patch description to avoid potential confusing in
the future.
OK, maybe the commit message can be changed to the following:
```
In offline_pages(), if a node becomes memoryless, we
will clear its N_MEMORY state by calling node_states_clear_node().
But we do this after rebuilding the zonelists by calling
build_all_zonelists(), which will cause this memoryless node to
still be in the fallback nodes (node_order[]) of other nodes.
To drop memoryless nodes from fallback nodes in this case, just
call node_states_clear_node() before calling build_all_zonelists().
In this way, we will not try to allocate pages from memoryless
node0, then the panic mentioned in [1] will also be fixed. Even though
this problem has been solved by dropping the NODE_MIN_SIZE constrain
in x86 [2], it would be better to fix it in the core MM as well.
[1].
https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@xxxxxxxxxxxxx/
[2]. https://lore.kernel.org/all/20231017062215.171670-1-rppt@xxxxxxxxxx/
```
Thanks,
Qi
--
Best Regards,
Huang, Ying
Thanks,
Qi
--
Best Regards,
Huang, Ying
This will incur
some runtime overhead.
To drop memoryless node from fallback lists in this case, just
call node_states_clear_node() before calling build_all_zonelists().
Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
[snip]
--
Best Regards,
Huang, Ying
