On Mon, Apr 8, 2024 at 7:20 PM Huang, Ying <ying.huang@xxxxxxxxx> wrote: > > Barry Song <21cnbao@xxxxxxxxx> writes: > > > From: Chuanhua Han <hanchuanhua@xxxxxxxx> > > > > When a large folio is found in the swapcache, the current implementation > > requires calling do_swap_page() nr_pages times, resulting in nr_pages > > page faults. This patch opts to map the entire large folio at once to > > minimize page faults. Additionally, redundant checks and early exits > > for ARM64 MTE restoring are removed. > > For large folios in reclaiming, it makes sense to restore all PTE > mappings to the large folio to reduce the number of page faults. > Indeed, this patch addresses the refault case first, much less controversial then :-) > But for large folios swapped in, I think that it's better to map one PTE > which triggers the page fault only. Because this makes us get the > opportunity to trap the page accesses to the sub-pages of the large > folio that is swapped in ahead (kind of swap readahead). Then we can > decide the order of large folio swapin based on the readahead window > information. That is, we may need to check PageReadahead() to decide > whether to map all PTEs in the future. Another scenario occurs when a process opts to utilize large folios for swap_readahead. Subsequently, another process encounters the large folios introduced by the former process. In this case, would it be optimal to fully map them just like the refault case? > > -- > Best Regards, > Huang, Ying Thanks Barry
