David Hildenbrand <david@xxxxxxxxxx> writes: > On 13.11.23 11:45, Baolin Wang wrote: >> Currently, the file pages already support large folio, and supporting for >> anonymous pages is also under discussion[1]. Moreover, the numa balancing >> code are converted to use a folio by previous thread[2], and the migrate_pages >> function also already supports the large folio migration. >> So now I did not see any reason to continue restricting NUMA >> balancing for >> large folio. > > I recall John wanted to look into that. CCing him. > > I'll note that the "head page mapcount" heuristic to detect sharers will > now strike on the PTE path and make us believe that a large folios is > exclusive, although it isn't. Even 4k folio may be shared by multiple processes/threads. So, numa balancing uses a multi-stage node selection algorithm (mostly implemented in should_numa_migrate_memory()) to identify shared folios. I think that the algorithm needs to be adjusted for PTE mapped large folio for shared folios. And, as a performance improvement patch, some performance data needs to be provided. And, the effect of shared folio detection needs to be tested too. -- Best Regards, Huang, Ying
