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

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

On 8/6/26 10:04 AM, Zi Yan wrote:
> On 5 Aug 2026, at 21:30, Baolin Wang wrote:
> 
>> 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:)
> 
> Sure. Or update usage() to print “mthp_khugepaged only supports anon”. You
> can remove that after you add other support types.

Ack. Thanks for all your valuable input:)