On Fri, Aug 29, 2025 at 08:09:53PM -0700, Andrew Morton wrote: >On Sat, 30 Aug 2025 02:31:02 +0000 Wei Yang <richard.weiy...@gmail.com> wrote: > >> The check of is_backed_by_folio() is done on each page. >> >> Directly move pointer to next page instead of increase one and check if >> it is page size aligned. > >Why? > >> --- a/tools/testing/selftests/mm/split_huge_page_test.c >> +++ b/tools/testing/selftests/mm/split_huge_page_test.c >> @@ -423,9 +423,8 @@ static void split_pte_mapped_thp(void) >> >> /* smap does not show THPs after mremap, use kpageflags instead */ >> thp_size = 0; >> - for (i = 0; i < pagesize * 4; i++) >> - if (i % pagesize == 0 && >> - is_backed_by_folio(&pte_mapped[i], pmd_order, pagemap_fd, >> kpageflags_fd)) >> + for (i = 0; i < pagesize * 4; i += pagesize) >> + if (is_backed_by_folio(&pte_mapped[i], pmd_order, pagemap_fd, >> kpageflags_fd)) >> thp_size++; > >Looks like we're doing more work. Is there something wrong with the >existing code?
Excuse me if I misunderstand the code. Originally, i iterate from 0 to pagesize * 4 one by one and call is_backed_by_folio() when i is 0, 4096, 8192, 12288. The change makes i just iterate on 0, 4096, 8192, 12288 and call is_backed_by_folio() respectively. Current code is not wrong, but not necessary to iterate one by one. -- Wei Yang Help you, Help me
