Re: [RFC PATCH v0 2/2] mm: sched: Batch-migrate misplaced pages

[Donet Tom <donettom@linux.ibm.com>]

On 5/22/25 10:09 AM, Bharata B Rao wrote:
> Hi Donet,
>
> On 21-May-25 11:55 PM, Donet Tom wrote:
>>
>>> +static void migrate_queued_pages(struct list_head *migrate_list)
>>> +{
>>> +    int cur_nid, nid;
>>> +    struct folio *folio, *tmp;
>>> +    LIST_HEAD(nid_list);
>>> +
>>> +    folio = list_entry(migrate_list, struct folio, lru);
>>> +    cur_nid = folio_last_cpupid(folio);
>>
>> Hi Bharatha,
>>
>> This is target node ID right?
>
> Correct.
>
>>
>>
>>> +
>>> +    list_for_each_entry_safe(folio, tmp, migrate_list, lru) {
>>> +        nid = folio_xchg_last_cpupid(folio, -1);
>>
>> Just one doubt: to get the last CPU ID (target node ID) here, 
>> folio_xchg_last_cpupid()
>>
>> is used, whereas earlier folio_last_cpupid() was used. Is there a 
>> specific reason for
>>
>> using different functions?
>
> This function iterates over the isolated folios looking for the same 
> target_nid so that all of them can be migrated at once to the given 
> target_nid. Hence the first call just reads the target_nid from 
> last_cpupid field to note which nid is of interest in the current 
> iteration and the next call actually reads target_nid and resets the 
> last_cpupid field.


Thank you, Bharata, for the clarification.

>
> Regards,
> Bharata.