Re: [PATCH v2 4/4] selftests: mm: add mTHP collapse test cases

[Baolin Wang <baolin.wang@linux.alibaba.com>]

On 8/6/26 9:25 AM, Zi Yan wrote:
> On 5 Aug 2026, at 21:17, Baolin Wang wrote:
> 
>> On 8/6/26 12:46 AM, Zi Yan wrote:
>>> On Sat Aug 1, 2026 at 2:26 AM EDT, Baolin Wang wrote:
>>>> Added a new command 'mthp_khugepaged' for mTHP collapse, along with the '-c'
>>>> parameter to specify the collapse order. Additionally, added mTHP collapse
>>>> test cases for 'collapse_full', 'collapse_empty', and 'collapse_single_mthp'
>>>> for anonymous folios. All khugepaged test cases passed.
>>>>
>>>> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>>>> ---
>>>>    tools/testing/selftests/mm/khugepaged.c   | 130 ++++++++++++++++++----
>>>>    tools/testing/selftests/mm/run_vmtests.sh |   2 +
>>>>    2 files changed, 113 insertions(+), 19 deletions(-)
>>>>
>>>> diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c
>>>> index f69be6be0ecd..64d6da6aa90d 100644
>>>> --- a/tools/testing/selftests/mm/khugepaged.c
>>>> +++ b/tools/testing/selftests/mm/khugepaged.c
>>>> @@ -26,9 +26,11 @@
>>>>     #define BASE_ADDR ((void *)(1UL << 30))
>>>>    static unsigned long hpage_pmd_size;
>>>> +static int hpage_pmd_order;
>>>>    static unsigned long page_size;
>>>>    static int hpage_pmd_nr;
>>>>    static int anon_order;
>>>> +static int collapse_order;
>>>
>>> <snip>
>>>
>>>>   diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
>>>> index 687d115e3bd8..d09f9f6a384e 100755
>>>> --- a/tools/testing/selftests/mm/run_vmtests.sh
>>>> +++ b/tools/testing/selftests/mm/run_vmtests.sh
>>>> @@ -410,6 +410,8 @@ CATEGORY="thp" run_test ./khugepaged all:shmem
>>>>     CATEGORY="thp" run_test ./khugepaged -s 4 all:shmem
>>>>   +CATEGORY="thp" run_test ./khugepaged -c 4 mthp_khugepaged:anon
>>>
>>> Why only testing collapse_order == 4? It is more useful to test all
>>> possible mTHP orders. -c can accept common separated order and a range.
>>
>> This also follows the previous '-s' parameter configuration, which is used to specify the mTHP order allocation.
>>
>> I think specifying a single order size already tests the overall mTHP collapse
> 
> Got it. If a single order covers the flow, I am fine with it.
> 
>> flow, so I'm not sure whether testing all orders is worthwhile. Maybe I can add a few more orders?
>> ./khugepaged -c 2 mthp_khugepaged:anon
>> ./khugepaged -c 4 mthp_khugepaged:anon
>> ./khugepaged -c 8 mthp_khugepaged:anon
>>
>>> Why only testing mthp_khugepaged:anon? IIRC, file and shmem are not
>>> supported, so khugepaged should reject them, right?
>>
>> Currently, I have not added test cases for shmem mTHP collapse, so adding file or shmem would be no-ops and might mislead others. I will add the shmem/file mTHP collapse feature and test cases in a following patchset.
> 
> Right. I mean when one specifies ./khugepaged mthp_khugepaged:file/shmem, the
> program should show some error like “file/shmem not supported”.

Yes, that works too. I still prefer to add the corresponding test cases 
after I add shmem mTHP collapse support:)

But if you have a strong opinion on this, I can also add a "not 
supported" message first.