Re: [PATCH RESEND v1 3/5] selftests/mm: skip khugepaged swap tests without swap

[Sarthak Sharma <sarthak.sharma@arm.com>]

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 <usama.anjum@arm.com>
> ---
>  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:

# 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);
>