Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> writes:
> On 2021/11/11 16:51, Huang, Ying wrote:
>> Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> writes:
>>
>>> For the worst case (MAX_NUMNODES=1024), the node_demotion structure can
>>> consume 32k bytes, which appears too large, so we can change to allocate
>>> node_demotion dynamically at initialization time. Meanwhile allocating
>>> the target demotion nodes array dynamically to select a suitable size
>>> according to the MAX_NUMNODES.
>>>
>>> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
>>> ---
>>> mm/migrate.c | 38 +++++++++++++++++++++++++++++---------
>>> 1 file changed, 29 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/mm/migrate.c b/mm/migrate.c
>>> index 126e9e6..0145b38 100644
>>> --- a/mm/migrate.c
>>> +++ b/mm/migrate.c
>>> @@ -1152,10 +1152,11 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
>>> #define DEFAULT_DEMOTION_TARGET_NODES 15
>>> struct demotion_nodes {
>>> unsigned short nr;
>>> - short nodes[DEFAULT_DEMOTION_TARGET_NODES];
>>> + short nodes[];
>>> };
>>> -static struct demotion_nodes node_demotion[MAX_NUMNODES]
>>> __read_mostly;
>>> +static struct demotion_nodes *node_demotion[MAX_NUMNODES] __read_mostly;
>>> +static unsigned short target_nodes_max;
>> I think we can use something as below,
>> #if MAX_NUMNODES < DEFAULT_DEMOTION_TARGET_NODES
>> #define DEMOTION_TARGET_NODES (MAX_NUMNODES - 1)
>> #else
>> #define DEMOTION_TARGET_NODES DEFAULT_DEMOTION_TARGET_NODES
>> #endif
>
> Yes, looks better.
>
>> static struct demotion_nodes *node_demotion;
>> Then we can allocate nr_node_ids * sizeof(struct demotion_nodes) for
>> node_demotion.
>
> Yeah, this is simple. The reason I want to declare the structure like
> "struct demotion_nodes *node_demotion[MAX_NUMNODES]" is that, we can
> validate the non-possible nodes which are invalid to demote memory,
> and in case the node_demotion[nid] is failed to be allocated which can
> be validated, though this is unlikely.
In case allocation failure, we can still check "node_demotion == NULL".
Best Regards,
Huang, Ying
> However, I agree with you to
> keep things simple now and can be merged into patch 1. Will do in next
> version. Thanks.
