On 5/13/21 7:42 PM, Zi Yan wrote:
> On 13 May 2021, at 3:20, Anshuman Khandual wrote:
>
>> Although the zero huge page is being shared across various processes, each
>> mapping needs to update its mm's MM_ANONPAGES stat by HPAGE_PMD_NR in order
>> to be consistent. This just updates the stats in set_huge_zero_page() after
>> the mapping gets created.
>
> In addition, MM_ANONPAGES stats should be decreased at zap_huge_pmd() and
Right, would something like this work ?
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 63ed6b2..776984d 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1678,6 +1678,7 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
} else if (is_huge_zero_pmd(orig_pmd)) {
zap_deposited_table(tlb->mm, pmd);
+ add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
spin_unlock(ptl);
tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
} else {
> __split_huge_pmd_locked() when the zero huge page mapping is removed from
> a process, right?
__split_huge_pmd_locked() calls __split_huge_zero_page_pmd() which will
replace a zero huge page with multiple (HPAGE_PMD_NR) zero small pages.
Why should MM_ANONPAGES stats change for the MM when the mapping is still
out there but in normal pages now.
>
>>
>> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>> Cc: Zi Yan <ziy@xxxxxxxxxx>
>> Cc: linux-mm@xxxxxxxxx
>> Cc: linux-kernel@xxxxxxxxxxxxxxx
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
>> ---
>> Should it update MM_SHMEM_PAGES instead ? Applies on latest mainline.
>
> zero huge page is added via do_huge_pmd_anonymous_page(), I think MM_ANONPAGES
> is appropriate.
Okay, sure.
>
>>
>> mm/huge_memory.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index 63ed6b25deaa..262703304807 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -706,6 +706,7 @@ static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
>> if (pgtable)
>> pgtable_trans_huge_deposit(mm, pmd, pgtable);
>> set_pmd_at(mm, haddr, pmd, entry);
>> + add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
>> mm_inc_nr_ptes(mm);
>> }
>>
>> --
>> 2.20.1
>
>
> —
> Best Regards,
> Yan Zi
>
