Hi Sarthak, > > > On 10/13/26 7:41 PM, Yeoreum Yun wrote: > >> Hi Yeoreum! > >> > >> On 10/13/26 4:07 PM, Yeoreum Yun wrote: > >>> HPAGE_SIZE and HPAGE_SHIFT macro is written based on the 4KB PAGE_SIZE. > >>> When this macro is used in some test, test result would be strange in > >>> the system where PAGE_SIZE is more then 4KB. > >>> > >>> Here is the example with transhuge-stress test with 16KB PAGE_SIZE: > >>> > >>> transhuge-stress: allocate 61073 transhuge pages, using 122146 MiB > >>> virtual memory and 1908 MiB of ram > >>> 3.292 s/loop, 0.054 ms/page, 37106.002 MiB/s 2566 succeed, 58507 > >>> failed, 2566 different pages > >>> 0.591 s/loop, 0.010 ms/page, 206850.792 MiB/s 0 succeed, 61073 > >>> failed, 0 different pages > >>> 0.527 s/loop, 0.009 ms/page, 231895.107 MiB/s 0 succeed, 61073 > >>> failed, 0 different pages > >>> 0.527 s/loop, 0.009 ms/page, 231839.704 MiB/s 0 succeed, 61073 > >>> failed, 0 different pages > >>> 0.528 s/loop, 0.009 ms/page, 231544.782 MiB/s 0 succeed, 61073 > >>> failed, 0 different pages > >>> 0.528 s/loop, 0.009 ms/page, 231462.074 MiB/s 0 succeed, 61073 > >>> failed, 0 different pages > >>> 0.527 s/loop, 0.009 ms/page, 231770.300 MiB/s 0 succeed, 61073 > >>> failed, 0 different pages > >>> ... > >>> ok 1 Completed > >>> > >>> Remove the HPAGE_SIZE and HPAGE_SHIFT macro and introduce pmd_pshift() > >>> helper to get the HPAGE_SHIFT properly. For HPAGE_SIZE, use pre-existing > >>> helper, pmd_psize(). > >>> > >>> Also, run the KSM_MERGE_TIME_HUGE_PAGES test with a size of 512 MiB, > >>> which is the least common multiple of the PMD sizes for 4 KiB, 16 KiB, > >>> and 64 KiB base pages. Since allocate_transhuge() allocates mappings in > >>> PMD-sized units, the test may fail with the previous size of 100 MiB, > >>> which is not a multiple of the PMD size when the base page size is > >>> 16 KiB or 64 KiB. > >>> > >>> After this patch, output of transhuge-stress: > >>> > >>> transhuge-stress: allocate 3817 transhuge pages, using 122146 MiB > >>> virtual memory and 119 MiB of ram > >>> 2.558 s/loop, 0.670 ms/page, 47755.759 MiB/s 2585 succeed, 1232 > >>> failed, 2585 different pages > >>> 2.640 s/loop, 0.692 ms/page, 46268.432 MiB/s 2585 succeed, 1232 > >>> failed, 2585 different pages > >>> 2.635 s/loop, 0.690 ms/page, 46360.298 MiB/s 2585 succeed, 1232 > >>> failed, 2585 different pages > >>> 2.782 s/loop, 0.729 ms/page, 43899.795 MiB/s 2616 succeed, 1201 > >>> failed, 2616 different pages > >>> 2.692 s/loop, 0.705 ms/page, 45380.876 MiB/s 2627 succeed, 1190 > >>> failed, 2627 different pages > >>> 2.612 s/loop, 0.684 ms/page, 46765.812 MiB/s 2628 succeed, 1189 > >>> failed, 2628 different pages > >>> 2.683 s/loop, 0.703 ms/page, 45520.990 MiB/s 2630 succeed, 1187 > >>> failed, 2630 different pages > >>> 2.727 s/loop, 0.714 ms/page, 44789.321 MiB/s 2631 succeed, 1186 > >>> failed, 2631 different pages > >>> ... > >>> ok 1 Completed > >>> > >>> Suggested-by: Lorenzo Stoakes (ARM) <[email protected]> > >>> Signed-off-by: Yeoreum Yun <[email protected]> > >>> --- > >>> tools/testing/selftests/mm/guard-regions.c | 10 +++++-- > >>> tools/testing/selftests/mm/ksm_tests.c | 16 ++++++----- > >>> tools/testing/selftests/mm/run_vmtests.sh | 4 +-- > >>> tools/testing/selftests/mm/transhuge-stress.c | 25 +++++++++++------- > >>> tools/testing/selftests/mm/vm_util.c | 38 > >>> +++++++++++++++++++++++---- > >>> tools/testing/selftests/mm/vm_util.h | 9 +++---- > >>> 6 files changed, 71 insertions(+), 31 deletions(-) > >>> > >>> diff --git a/tools/testing/selftests/mm/guard-regions.c > >>> b/tools/testing/selftests/mm/guard-regions.c > >>> index f7d53ea3c2527..02f69244f9a42 100644 > >>> --- a/tools/testing/selftests/mm/guard-regions.c > >>> +++ b/tools/testing/selftests/mm/guard-regions.c > >>> @@ -2194,14 +2194,20 @@ TEST_F(guard_regions, pagemap_scan) > >>> TEST_F(guard_regions, collapse) > >>> { > >>> const unsigned long page_size = self->page_size; > >>> - const unsigned long size = 2 * HPAGE_SIZE; > >>> - const unsigned long num_pages = size / page_size; > >>> + const uint64_t hpage_size = pmd_psize(); > >>> + unsigned long size, num_pages; > >>> char *ptr; > >>> int i; > >>> > >>> if (!thp_available()) > >>> SKIP(return, "Transparent Hugepages not available\n"); > >>> > >>> + if (!hpage_size) > >>> + ksft_exit_fail_msg("reading hpage_size failed\n"); > >> > >> I'm sorry for not catching this earlier, but I don't think calling a > >> ksft_exit_fail_msg() for not being able to calculate PMD size is a good > >> idea. Maybe call an ASSERT*() here, something like > >> > >> ASSERT_NE(hpage_size, 0); > >> > >> so that just this test fails, instead of the whole run exiting with a > >> bail out? > > > > No. The failure would occur if open() or read() fails, and subsequent > > attempts would likely fail for the same reason. > > I think I couldn't clearly explain my concern. Let me put it again, > please let me know if I am missing something. > > I was mistaken, on checking I found that guard_regions runs each test in > a separate child process. So calling ksft_exit_fail_msg() won't exit the > whole test run. > > To reproduce the case, I bind mounted /dev/null over > /sys/kernel/mm/transparent_hugepage/hpage_pmd_size in a QEMU so that > pmd_psize() returns 0. Then on running ./guard_regions (your patches > applied), I got this output (putting relevant section of that since the > log is quite long): > > > # RUN guard_regions.anon.collapse ... > Bail out! reading hpage_size failed > # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0 > # collapse: Test failed > # FAIL guard_regions.anon.collapse > not ok 29 guard_regions.anon.collapse > . > . > ok 58 guard_regions.shmem.pagemap_scan > # RUN guard_regions.shmem.collapse ... > Bail out! reading hpage_size failed > # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0 > # collapse: Test failed > # FAIL guard_regions.shmem.collapse > not ok 59 guard_regions.shmem.collapse > . > . > # RUN guard_regions.file.collapse ... > Bail out! reading hpage_size failed > # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0 > # collapse: Test failed > # FAIL guard_regions.file.collapse > not ok 89 guard_regions.file.collapse > # RUN guard_regions.file.smaps ... > # OK guard_regions.file.smaps > ok 90 guard_regions.file.smaps > # FAILED: 87 / 90 tests passed. > # 19 skipped test(s) detected. Consider enabling relevant config options > to improve coverage. > # Totals: pass:68 fail:3 xfail:0 xpass:0 skip:19 error:0 > > > which looks weird with all the bailouts. On the other hand, if we > replace the ksft_exit_fail_msg() with ASSERT_NE(), here's the output we get: > > > # RUN guard_regions.anon.collapse ... > # guard-regions.c:2205:collapse:Expected hpage_size (0) != 0 (0) > # collapse: Test terminated by assertion > # FAIL guard_regions.anon.collapse > not ok 29 guard_regions.anon.collapse > . > . > ok 58 guard_regions.shmem.pagemap_scan > # RUN guard_regions.shmem.collapse ... > # guard-regions.c:2205:collapse:Expected hpage_size (0) != 0 (0) > # collapse: Test terminated by assertion > # FAIL guard_regions.shmem.collapse > not ok 59 guard_regions.shmem.collapse > . > . > # RUN guard_regions.file.collapse ... > # guard-regions.c:2205:collapse:Expected hpage_size (0) != 0 (0) > # collapse: Test terminated by assertion > # FAIL guard_regions.file.collapse > not ok 89 guard_regions.file.collapse > # RUN guard_regions.file.smaps ... > # OK guard_regions.file.smaps > ok 90 guard_regions.file.smaps > # FAILED: 87 / 90 tests passed. > # 19 skipped test(s) detected. Consider enabling relevant config options > to improve coverage. > # Totals: pass:68 fail:3 xfail:0 xpass:0 skip:19 error:0 > > So the issue is not as severe as I'd thought. It can be argued that this > is very less likely to happen. But yeah, I feel changing it would be > better as it is more suitable with the ksefltest_harness and would give > a cleaner TAP output incase this happens. Rest I leave it to you and > other folks to decide whether this needs to be changed :).
Still I don't think it would be more suitable with kselftest_harness. Anyway what I can see it's a only difference of the *message* -- "Bail out! reading hpage_size failed" vs "Expected hpage_size (0) != 0 (0)" TBH, I don't think this difference makes the TAP output any cleaner. I think it's sufficient as long as the message clearly explains the reason for the failure. -- Sincerely, Yeoreum Yun
