On 7/22/26 7:35 PM, Muhammad Usama Anjum wrote:
> Hi,
>
> Thank you for review.
>
> On 22/07/2026 1:16 pm, Sarthak Sharma wrote:
>> Hi Usama!
>>
>> On 7/22/26 2:41 PM, Muhammad Usama Anjum wrote:
>>> collapse_swapin_single_pte and collapse_max_ptes_swap require
>>> MADV_PAGEOUT to replace anonymous pages with swap entries. On swapless
>>> systems there is no backing store with which to create those entries, so
>>> check_swap() reports missing setup rather than broken khugepaged behavior.
>>>
>>> Swapless configurations are common on Android and other constrained
>>> test devices. Failing these cases obscures actionable results from the
>>> rest of the khugepaged suite.
>>>
>>> Check /proc/swaps before either swap-dependent case and skip when no
>>> active swap area exists. With swap present, retain the existing
>>> MADV_PAGEOUT and swap-entry assertions unchanged.
>>>
>>> Signed-off-by: Muhammad Usama Anjum <[email protected]>
>>> ---
>>> tools/testing/selftests/mm/khugepaged.c | 34 +++++++++++++++++++++++++
>>> 1 file changed, 34 insertions(+)
>>>
>>> diff --git a/tools/testing/selftests/mm/khugepaged.c
>>> b/tools/testing/selftests/mm/khugepaged.c
>>> index 10e8dedcb087d..a152cec59fcbd 100644
>>> --- a/tools/testing/selftests/mm/khugepaged.c
>>> +++ b/tools/testing/selftests/mm/khugepaged.c
>>> @@ -100,6 +100,28 @@ static void skip(const char *msg)
>>> exit_status = KSFT_SKIP;
>>> }
>>>
>>> +static bool is_swap_enabled(void)
>>> +{
>>> + char buf[MAX_LINE_LENGTH];
>>> + FILE *file;
>>> + bool enabled = false;
>>> +
>>> + file = fopen("/proc/swaps", "r");
>>> + if (!file)
>>> + return false;
>>> +
>>> + if (!fgets(buf, sizeof(buf), file))
>>> + goto out;
>>> +
>>> + /* Check for first active swap entry. */
>>> + if (fgets(buf, sizeof(buf), file))
>>> + enabled = true;
>>> +
>>> +out:
>>> + fclose(file);
>>> + return enabled;
>>> +}
>>> +
>>> static void save_settings(void)
>>> {
>>> ksft_print_msg("Save THP and khugepaged settings...");
>>> @@ -734,6 +756,12 @@ static void collapse_swapin_single_pte(struct
>>> collapse_context *c, struct mem_op
>>> {
>>> void *p;
>>>
>>> + if (!is_swap_enabled()) {
>>> + skip("No active swap");
>>
>> Can we prefix this skip message with a #, as recommended for KTAP
>> output? Right now it is printing like this:
> It looks like `skip()` is not being prefixed with `#` in this test
> because of how it is currently used.
>
> The `skip()` helper itself should probably be fixed, but that can be
> handled in a separate follow-up patch. This test is not fully
> TAP-compliant at the moment: the normal pass/fail output appears to be
> compliant, while the skip-related messages are not. Would it make sense
> to address that separately from this series?
I think there's nothing wrong with the skip() helper. Normal pass/fail
output appears to be TAP compliant because there's a ksft_print_msg(...)
call before calling pass()/fail() helpers. If we move the
ksft_print_msg() line before the is_swap_enabled() check, we'll get
output which is TAP compliant, something like this:
# Run test: collapse_swapin_single_pte (khugepaged:anon)
# Swapout one page... No active swap
ok 16 # SKIP collapse_swapin_single_pte
#
# Run test: collapse_swapin_single_pte (madvise:anon)
# Swapout one page... No active swap
ok 17 # SKIP collapse_swapin_single_pte
#
# Run test: collapse_max_ptes_swap (khugepaged:anon)
# Swapout 65 of 512 pages... No active swap
ok 18 # SKIP collapse_max_ptes_swap
#
# Run test: collapse_max_ptes_swap (madvise:anon)
# Swapout 65 of 512 pages... No active swap
ok 19 # SKIP collapse_max_ptes_swap
>
> Also when we run the whole mm suite using ./run_vmtests.sh, it appends an
> extra
> # in start of the output which we get by running normal test directly. Its
> controversial already that we are applying TAP styling to suite level and test
> level as well. So non-compliant skip in this test makes overall output
> compliant.>
>>
>> # Run test: collapse_swapin_single_pte (khugepaged:anon)
>> No active swap
>> ok 16 # SKIP collapse_swapin_single_pte
>> #
>> # Run test: collapse_swapin_single_pte (madvise:anon)
>> No active swap
>> ok 17 # SKIP collapse_swapin_single_pte
>> #
>> # Run test: collapse_max_ptes_swap (khugepaged:anon)
>> No active swap
>> ok 18 # SKIP collapse_max_ptes_swap
>> #
>> # Run test: collapse_max_ptes_swap (madvise:anon)
>> No active swap
>>
>>
>>> + ksft_test_result_report(exit_status, "%s\n", __func__);
>>> + return;
>>> + }
>>> +
>>> p = ops->setup_area(1);
>>> ops->fault(p, 0, hpage_pmd_size);
>>>
>>> @@ -760,6 +788,12 @@ static void collapse_max_ptes_swap(struct
>>> collapse_context *c, struct mem_ops *o
>>> int max_ptes_swap = thp_read_num("khugepaged/max_ptes_swap");
>>> void *p;
>>>
>>> + if (!is_swap_enabled()) {
>>> + skip("No active swap");
>>
>> Same here.
>>
>>> + ksft_test_result_report(exit_status, "%s\n", __func__);
>>> + return;
>>> + }
>>> +
>>> p = ops->setup_area(1);
>>> ops->fault(p, 0, hpage_pmd_size);
>>>
>>
>
