linux-kernel - Re: [PATCH v7 03/12] khugepaged: generalize hugepage_vma

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Message-ID: <89733427-8cc4-46d2-8a4f-19a621d8ab7b@arm.com>
Date: Wed, 28 May 2025 12:27:38 +0530
From: Dev Jain <dev.jain@....com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>,
 Nico Pache <npache@...hat.com>, linux-mm@...ck.org,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Cc: david@...hat.com, ziy@...dia.com, lorenzo.stoakes@...cle.com,
 Liam.Howlett@...cle.com, ryan.roberts@....com, corbet@....net,
 rostedt@...dmis.org, mhiramat@...nel.org, mathieu.desnoyers@...icios.com,
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 peterx@...hat.com, wangkefeng.wang@...wei.com, usamaarif642@...il.com,
 sunnanyong@...wei.com, vishal.moola@...il.com,
 thomas.hellstrom@...ux.intel.com, yang@...amperecomputing.com,
 kirill.shutemov@...ux.intel.com, aarcange@...hat.com, raquini@...hat.com,
 anshuman.khandual@....com, catalin.marinas@....com, tiwai@...e.de,
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Subject: Re: [PATCH v7 03/12] khugepaged: generalize hugepage_vma_revalidate
 for mTHP support


On 23/05/25 12:25 pm, Baolin Wang wrote:
>
>
> On 2025/5/15 11:22, Nico Pache wrote:
>> For khugepaged to support different mTHP orders, we must generalize this
>> to check if the PMD is not shared by another VMA and the order is
>> enabled.
>>
>> No functional change in this patch.
>>
>> Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
>> Co-developed-by: Dev Jain <dev.jain@....com>
>> Signed-off-by: Dev Jain <dev.jain@....com>
>> Signed-off-by: Nico Pache <npache@...hat.com>
>> ---
>>   mm/khugepaged.c | 10 +++++-----
>>   1 file changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
>> index 5457571d505a..0c4d6a02d59c 100644
>> --- a/mm/khugepaged.c
>> +++ b/mm/khugepaged.c
>> @@ -920,7 +920,7 @@ static int khugepaged_find_target_node(struct 
>> collapse_control *cc)
>>   static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned 
>> long address,
>>                      bool expect_anon,
>>                      struct vm_area_struct **vmap,
>> -                   struct collapse_control *cc)
>> +                   struct collapse_control *cc, int order)
>>   {
>>       struct vm_area_struct *vma;
>>       unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS 
>> : 0;
>> @@ -934,7 +934,7 @@ static int hugepage_vma_revalidate(struct 
>> mm_struct *mm, unsigned long address,
>>         if (!thp_vma_suitable_order(vma, address, PMD_ORDER))
>
> Sorry, I missed this before. Should we also change 'PMD_ORDER' to 
> 'order' for the thp_vma_suitable_order()?


You are right, I did that in my patch:

https://lore.kernel.org/all/20250211111326.14295-3-dev.jain@arm.com/


>
>>           return SCAN_ADDRESS_RANGE;
>> -    if (!thp_vma_allowable_order(vma, vma->vm_flags, tva_flags, 
>> PMD_ORDER))
>> +    if (!thp_vma_allowable_order(vma, vma->vm_flags, tva_flags, order))
>>           return SCAN_VMA_CHECK;
>>       /*
>>        * Anon VMA expected, the address may be unmapped then
>> @@ -1130,7 +1130,7 @@ static int collapse_huge_page(struct mm_struct 
>> *mm, unsigned long address,
>>           goto out_nolock;
>>         mmap_read_lock(mm);
>> -    result = hugepage_vma_revalidate(mm, address, true, &vma, cc);
>> +    result = hugepage_vma_revalidate(mm, address, true, &vma, cc, 
>> HPAGE_PMD_ORDER);
>>       if (result != SCAN_SUCCEED) {
>>           mmap_read_unlock(mm);
>>           goto out_nolock;
>> @@ -1164,7 +1164,7 @@ static int collapse_huge_page(struct mm_struct 
>> *mm, unsigned long address,
>>        * mmap_lock.
>>        */
>>       mmap_write_lock(mm);
>> -    result = hugepage_vma_revalidate(mm, address, true, &vma, cc);
>> +    result = hugepage_vma_revalidate(mm, address, true, &vma, cc, 
>> HPAGE_PMD_ORDER);
>>       if (result != SCAN_SUCCEED)
>>           goto out_up_write;
>>       /* check if the pmd is still valid */
>> @@ -2782,7 +2782,7 @@ int madvise_collapse(struct vm_area_struct 
>> *vma, struct vm_area_struct **prev,
>>               mmap_read_lock(mm);
>>               mmap_locked = true;
>>               result = hugepage_vma_revalidate(mm, addr, false, &vma,
>> -                             cc);
>> +                             cc, HPAGE_PMD_ORDER);
>>               if (result  != SCAN_SUCCEED) {
>>                   last_fail = result;
>>                   goto out_nolock;