Re: [PATCH v2 4/7] mm/selftests: Fix split_huge_page_test failure on systems with 64KB page size

[Donet Tom <donettom@linux.ibm.com>]

On 7/3/25 8:00 PM, Zi Yan wrote:
> On 3 Jul 2025, at 2:06, Aboorva Devarajan wrote:
>
>> From: Donet Tom <donettom@linux.ibm.com>
>>
>> The split_huge_page_test fails on systems with a 64KB base page size.
>> This is because the order of a 2MB huge page is different:
>>
>> On 64KB systems, the order is 5.
>>
>> On 4KB systems, it's 9.
>>
>> The test currently assumes a maximum huge page order of 9, which is only
>> valid for 4KB base page systems. On systems with 64KB pages, attempting
>> to split huge pages beyond their actual order (5) causes the test to fail.
>>
>> In this patch, we calculate the huge page order based on the system's base
>> page size. With this change, the tests now run successfully on both 64KB
>> and 4KB page size systems.
>>
>> Fixes: fa6c02315f745 ("mm: huge_memory: a new debugfs interface for splitting THP tests")
>> Signed-off-by: Donet Tom <donettom@linux.ibm.com>
>> Signed-off-by: Aboorva Devarajan <aboorvad@linux.ibm.com>
>> ---
>>   .../selftests/mm/split_huge_page_test.c       | 23 ++++++++++++++-----
>>   1 file changed, 17 insertions(+), 6 deletions(-)
>>
>> diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
>> index aa7400ed0e99..38296a758330 100644
>> --- a/tools/testing/selftests/mm/split_huge_page_test.c
>> +++ b/tools/testing/selftests/mm/split_huge_page_test.c
>> @@ -514,6 +514,15 @@ void split_thp_in_pagecache_to_order_at(size_t fd_size, const char *fs_loc,
>>   	}
>>   }
>>
>> +static unsigned int get_order(unsigned int pages)
>> +{
>> +	unsigned int order = 0;
>> +
>> +	while ((1U << order) < pages)
>> +		order++;
>> +	return order;
>> +}
>> +
>>   int main(int argc, char **argv)
>>   {
>>   	int i;
>> @@ -523,6 +532,7 @@ int main(int argc, char **argv)
>>   	const char *fs_loc;
>>   	bool created_tmp;
>>   	int offset;
>> +	unsigned int max_order;
>>
>>   	ksft_print_header();
>>
>> @@ -534,32 +544,33 @@ int main(int argc, char **argv)
>>   	if (argc > 1)
>>   		optional_xfs_path = argv[1];
>>
>> -	ksft_set_plan(1+8+1+9+9+8*4+2);
>> -
>>   	pagesize = getpagesize();
>>   	pageshift = ffs(pagesize) - 1;
>>   	pmd_pagesize = read_pmd_pagesize();
>>   	if (!pmd_pagesize)
>>   		ksft_exit_fail_msg("Reading PMD pagesize failed\n");
>>
>> +	max_order = get_order(pmd_pagesize/pagesize);
> pmd_pagesize/pagesize is reused below, a tmp variable would be good.


Thank you. I will add it in next version.


>
>> +	ksft_set_plan(1+(max_order-1)+1+max_order+max_order+(max_order-1)*4+2);
>> +
>>   	fd_size = 2 * pmd_pagesize;
>>
>>   	split_pmd_zero_pages();
>>
>> -	for (i = 0; i < 9; i++)
>> +	for (i = 0; i < max_order; i++)
>>   		if (i != 1)
>>   			split_pmd_thp_to_order(i);
>>
>>   	split_pte_mapped_thp();
>> -	for (i = 0; i < 9; i++)
>> +	for (i = 0; i < max_order; i++)
>>   		split_file_backed_thp(i);
>>
>>   	created_tmp = prepare_thp_fs(optional_xfs_path, fs_loc_template,
>>   			&fs_loc);
>> -	for (i = 8; i >= 0; i--)
>> +	for (i = (max_order-1); i >= 0; i--)
>>   		split_thp_in_pagecache_to_order_at(fd_size, fs_loc, i, -1);
>>
>> -	for (i = 0; i < 9; i++)
>> +	for (i = 0; i < max_order; i++)
>>   		for (offset = 0;
>>   		     offset < pmd_pagesize / pagesize;
>>   		     offset += MAX(pmd_pagesize / pagesize / 4, 1 << i))
> With the change to get_order() proposed by David and ksft_set_plan()
> simplification, Reviewed-by: Zi Yan <ziy@nvidia.com>
>
> Best Regards,
> Yan, Zi